Table of contents

A joint analysis of the clustering of galaxies and their weak gravitational lensing signal is well-suited to simultaneously constrain the galaxy–halo connection as well as the cosmological parameters by breaking the degeneracy between galaxy bias and the amplitude of clustering signal. In a series of two papers, we perform such an analysis at the highest redshift ($z\sim 0.53$) in the literature using CMASS galaxies in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Eleventh Data Release (BOSS DR11) catalog spanning 8300 deg². In this paper, we present details of the clustering and weak lensing measurements of these galaxies. We define a subsample of 400,916 CMASS galaxies based on their redshifts and stellar-mass estimates so that the galaxies constitute an approximately volume-limited and similar population over the redshift range $0.47\leqslant z\leqslant 0.59$. We obtain a signal-to-noise ratio (S/N) $\simeq \;56$ for the galaxy clustering measurement. We also explore the redshift and stellar-mass dependence of the clustering signal. For the weak lensing measurement, we use existing deeper imaging data from the Canada–France–Hawaii Telescope Legacy Survey with publicly available shape and photometric redshift catalogs from CFHTLenS, but only in a 105 deg² area that overlaps with BOSS. This restricts the lensing measurement to only 5084 CMASS galaxies. After careful systematic tests, we find a highly significant detection of the CMASS weak lensing signal, with total S/N $\simeq \;26$. These measurements form the basis of the halo occupation distribution and cosmology analysis presented in More et al. (Paper II).

We perform a joint analysis of the abundance, the clustering, and the galaxy–galaxy lensing signal of galaxies measured from Data Release 11 of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey in our companion paper, Miyatake et al. The lensing signal was obtained by using the shape catalog of background galaxies from the Canada France Hawaii Telescope Legacy Survey, which was made publicly available by the CFHTLenS collaboration, with an area overlap of about 105 deg². We analyze the data in the framework of the halo model in order to fit halo occupation parameters and cosmological parameters (Ω$_{m}$ and ${{\sigma }_{8}}$) to these observables simultaneously, and thus break the degeneracy between galaxy bias and cosmology. Adopting a flat ΛCDM cosmology with priors on Ω$_{b}{{h}^{2}}$, ${{n}_{{\rm s}}}$, and h from the analysis of WMAP 9 yr data, we obtain constraints on the stellar mass–halo mass relation of galaxies in our sample. Marginalizing over the halo occupation distribution parameters and a number of other nuisance parameters in our model, we obtain Ω$_{m}=0.310_{-0.020}^{+0.019}$ and ${{\sigma }_{8}}=0.785_{-0.044}^{+0.044}$ (68% confidence). We demonstrate the robustness of our results with respect to sample selection and a variety of systematics such as the halo off-centering effect and possible incompleteness in our sample. Our constraints are consistent, complementary, and competitive with those obtained using other independent probes of these cosmological parameters. The cosmological analysis is the first of its kind to be performed at a redshift as high as 0.53.

There is ongoing debate regarding the extent that environment affects galaxy size growth beyond z ≥ 1. To investigate the differences in star-forming and quiescent galaxy properties as a function of environment at z = 2.1, we create a mass-complete sample of 59 cluster galaxies and 478 field galaxies with log(M_*/${{M}_{\odot }}$) ≥ 9 using photometric redshifts from the ZFOURGE survey. We compare the mass–size relation of field and cluster galaxies using measured galaxy semi-major axis half-light radii (${{r}_{1/2,{\rm maj}}}$) from CANDELS Hubble Space Telescope (HST)/F160W imaging. We find consistent mass-normalized (log(M_*/${{M}_{\odot }}$) = 10.7) sizes for quiescent field galaxies (${{r}_{1/2,{\rm maj}}}=1.81\pm 0.29$ kpc) and quiescent cluster galaxies (${{r}_{1/2,{\rm maj}}}=2.17\pm 0.63$ kpc). The mass-normalized size of star-forming cluster galaxies (${{r}_{1/2,{\rm maj}}}=4.00\pm 0.26$ kpc) is 12% larger (Kolmogorov–Smirnov (KS) test $2.1\sigma$) than star-forming field galaxies (${{r}_{1/2,{\rm maj}}}=3.57\pm 0.10$ kpc). From the mass–color relation we find that quiescent field galaxies with 9.7 < log(M_*/${{M}_{\odot }}$) $\leqslant \;10.4$ are slightly redder (KS test 3.6σ) than quiescent cluster galaxies, while cluster and field quiescent galaxies with log(M_*/${{M}_{\odot }}$) > 10.4 have consistent colors. We find that star-forming cluster galaxies are on average 20% redder than star-forming field galaxies at all masses. Furthermore, we stack galaxy images to measure average radial color profiles as a function of mass. Negative color gradients are only present for massive star-forming field and cluster galaxies with log(M_*/${{M}_{\odot }}$) $\gt \;10.4$; the remaining galaxy masses and types have flat profiles. Our results suggest, given the observed differences in size and color of star-forming field and cluster galaxies, that the environment has begun to influence/accelerate their evolution. However, the lack of differences between field and cluster quiescent galaxies indicates that the environment has not begun to significantly influence their evolution at z ∼ 2.

We present a new determination of the concentration–mass (c–M) relation for galaxy clusters based on our comprehensive lensing analysis of 19 X-ray selected galaxy clusters from the Cluster Lensing and Supernova Survey with Hubble (CLASH). Our sample spans a redshift range between 0.19 and 0.89. We combine weak-lensing constraints from the Hubble Space Telescope (HST) and from ground-based wide-field data with strong lensing constraints from HST. The results are reconstructions of the surface-mass density for all CLASH clusters on multi-scale grids. Our derivation of Navarro–Frenk–White parameters yields virial masses between $0.53\times {{10}^{15}}\;{{M}_{\odot }}/h$ and $1.76\times {{10}^{15}}\;{{M}_{\odot }}/h$ and the halo concentrations are distributed around ${{c}_{200c}}\sim 3.7$ with a $1\sigma$ significant negative slope with cluster mass. We find an excellent 4% agreement in the median ratio of our measured concentrations for each cluster and the respective expectation from numerical simulations after accounting for the CLASH selection function based on X-ray morphology. The simulations are analyzed in two dimensions to account for possible biases in the lensing reconstructions due to projection effects. The theoretical c–M relation from our X-ray selected set of simulated clusters and the c–M relation derived directly from the CLASH data agree at the 90% confidence level.

We report detections of new exoplanets from a radial-velocity (RV) survey of metal-rich FGK stars by using three telescopes. By optimizing our RV analysis method to long time-baseline observations, we have succeeded in detecting five new Jovian planets around three metal-rich stars, HD 1605, HD 1666, and HD 67087, with masses of $1.3\;{{M}_{\odot }}$, $1.5\;{{M}_{\odot }}$, and $1.4\;{{M}_{\odot }}$, respectively. A K1 subgiant star, HD 1605 hosts two planetary companions with minimum masses of ${{M}_{p}}{\rm sin} i=0.96{{M}_{{\rm Jup}}}$ and $3.5{{M}_{{\rm Jup}}}$ in circular orbits with the planets' periods $P=577.9$ and 2111 days, respectively. HD 1605 shows a significant linear trend in RVs. Such a system consisting of Jovian planets in circular orbits has rarely been found and thus HD 1605 should be an important example of a multi-planetary system that is likely unperturbed by planet–planet interactions. HD 1666 is an F7 main-sequence star that hosts an eccentric and massive planet of ${{M}_{p}}{\rm sin} i=6.4{{M}_{{\rm Jup}}}$ in an orbit with ${{a}_{p}}=0.94$ AU and eccentricity $e=0.63$. Such an eccentric and massive planet can be explained as a result of planet–planet interactions among Jovian planets. While we have found large residuals of ${\rm rms}=35.6\;{\rm m}\;{{{\rm s}}^{-1}}$, the periodogram analysis does not support any additional periodicities. Finally, HD 67087 hosts two planets of ${{M}_{p}}{\rm sin} i=3.1{{M}_{{\rm Jup}}}$ and $4.9{{M}_{{\rm Jup}}}$ in orbits with $P=352.2$ and 2374 days, and $e=0.17$ and 0.76, respectively. Although the current RVs do not lead to accurate determinations of its orbit and mass, HD 67087 c can be one of the most eccentric planets ever discovered in multiple systems.

In the first three years of operation, the Kepler mission found 3697 planet candidates (PCs) from a set of 18,406 transit-like features detected on more than 200,000 distinct stars. Vetting candidate signals manually by inspecting light curves and other diagnostic information is a labor intensive effort. Additionally, this classification methodology does not yield any information about the quality of PCs; all candidates are as credible as any other. The torrent of exoplanet discoveries will continue after Kepler, because a number of exoplanet surveys will have an even broader search area. This paper presents the application of machine-learning techniques to the classification of the exoplanet transit-like signals present in the Kepler light curve data. Transit-like detections are transformed into a uniform set of real-numbered attributes, the most important of which are described in this paper. Each of the known transit-like detections is assigned a class of PC; astrophysical false positive; or systematic, instrumental noise. We use a random forest algorithm to learn the mapping from attributes to classes on this training set. The random forest algorithm has been used previously to classify variable stars; this is the first time it has been used for exoplanet classification. We are able to achieve an overall error rate of 5.85% and an error rate for classifying exoplanets candidates of 2.81%.

RCW 120 is a Galactic H ii region that has a beautiful ring shape that is bright in the infrared. Our new CO J = 1–0 and J = 3–2 observations performed with the NANTEN2, Mopra, and ASTE telescopes have revealed that two molecular clouds with a velocity separation of 20 km s⁻¹ are both physically associated with RCW 120. The cloud at −8 km s⁻¹ apparently traces the infrared ring, while the other cloud at −28 km s⁻¹ is distributed just outside the opening of the infrared ring, interacting with the H ii region as suggested by the high kinetic temperature of the molecular gas and by the complementary distribution with the ionized gas. A spherically expanding shell driven by the H ii region is usually considered to be the origin of the observed ring structure in RCW 120. Our observations, however, indicate no evidence of the expanding motion in the velocity space, which is inconsistent with the expanding shell model. We postulate an alternative that, by applying the model introduced by Habe & Ohta, the exciting O star in RCW 120 was formed by a collision between the present two clouds at a collision velocity of ∼30 km s⁻¹. In the model, the observed infrared ring can be interpreted as the cavity created in the larger cloud by the collision, whose inner surface is illuminated by the strong ultraviolet radiation after the birth of the O star. We discuss that the present cloud–cloud collision scenario explains the observed signatures of RCW 120, i.e., its ring morphology, coexistence of the two clouds and their large velocity separation, and absence of the expanding motion.

We report on four large filament eruptions (FEs) from solar cycles 23 and 24 that were associated with large solar energetic particle (SEP) events and interplanetary type II radio bursts. The post-eruption arcades corresponded mostly to C-class soft X-ray enhancements, but an M1.0 flare was associated with one event. However, the associated coronal mass ejections (CMEs) were fast (speeds ∼ 1000 km s⁻¹) and appeared as halo CMEs in the coronagraph field of view. The interplanetary type II radio bursts occurred over a wide wavelength range, indicating the existence of strong shocks throughout the inner heliosphere. No metric type II bursts were present in three events, indicating that the shocks formed beyond 2–3 Rs. In one case, there was a metric type II burst with low starting frequency, indicating a shock formation height of ∼2 Rs. The FE-associated SEP events did have softer spectra (spectral index >4) in the 10–100 MeV range, but there were other low-intensity SEP events with spectral indices ≥4. Some of these events are likely FE-SEP events, but were not classified as such in the literature because they occurred close to active regions. Some were definitely associated with large active region flares, but the shock formation height was large. We definitely find a diminished role for flares and complex type III burst durations in these large SEP events. Fast CMEs and shock formation at larger distances from the Sun seem to be the primary characteristics of the FE-associated SEP events.

We investigate the sequence of events leading to the solar X1 flare SOL2014-03-29T17:48. Because of the unprecedented joint observations of an X-flare with the ground-based Dunn Solar Telescope and the spacecraft IRIS, Hinode, RHESSI, STEREO, and the Solar Dynamics Observatory, we can sample many solar layers from the photosphere to the corona. A filament eruption was observed above a region of previous flux emergence, which possibly led to a change in magnetic field configuration, causing the X-flare. This was concluded from the timing and location of the hard X-ray emission, which started to increase slightly less than a minute after the filament accelerated. The filament showed Doppler velocities of ∼2–5 km s⁻¹ at chromospheric temperatures for at least one hour before the flare occurred, mostly blueshifts, but also redshifts near its footpoints. Fifteen minutes before the flare, its chromospheric Doppler shifts increased to ∼6–10 km s⁻¹ and plasma heating could be observed before it lifted off with at least 600 km s⁻¹ as seen in IRIS data. Compared to previous studies, this acceleration (∼3–5 km s⁻²) is very fast, while the velocities are in the common range for coronal mass ejections. An interesting feature was a low-lying twisted second filament near the erupting filament, which did not seem to participate in the eruption. After the flare ribbons started on each of the second filament's sides, it seems to have untangled and vanished during the flare. These observations are some of the highest resolution data of an X-class flare to date and reveal some small-scale features yet to be explained.

The effects of magnetic field on stellar differential rotation (DR) are studied by comparing magnetohydrodynamic (MHD) models and their hydrodynamic (HD) counterparts in the broad range of rotation rates and across varying initial rotation profiles. Fully compressible MHD simulations of rotating penetrative convection are performed in a full-spherical shell geometry. Critical conditions for the transition of the DR between a faster equator (solar type) and a slower equator (anti-solar type) are explored by focusing on the "Rossby number (Ro)" and the "convective Rossby number (${\rm R}{{{\rm o}}_{{\rm conv}}}$)." It is confirmed that the transition is more gradual and the critical value for it is higher in the MHD model than in the HD model in view of the ${\rm R}{{{\rm o}}_{{\rm conv}}}$ dependence. As observed in earlier studies, the rotation profile shows a bistability near the transition in the HD model, whereas it disappears when allowing the growth of magnetic fields except in the model taking the anti-solar-type solution as the initial condition. We find that the transition occurs at ${\rm Ro}\simeq 1$ both in the MHD and HD models independently of the hysteresis. Not only the critical value but also the sharpness of the transition is similar between the two models in view of the Ro dependence. The influences of the dynamo-generated magnetic field and/or the hysteresis on convective motion are reflected by Ro. This is why the transition is unified in view of the Ro dependence. We also discuss the Ro dependence of magnetic dynamo activities with emphasis on their possible relation to the kinetic helicity profile.

We study 14 large solar jets observed in polar coronal holes. In EUV movies from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), each jet appears similar to most X-ray jets and EUV jets that erupt in coronal holes; but each is exceptional in that it goes higher than most, so high that it is observed in the outer corona beyond 2.2 R_Sun in images from the Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph (LASCO)/C2 coronagraph. From AIA He ii 304 Å movies and LASCO/C2 running-difference images of these high-reaching jets, we find: (1) the front of the jet transits the corona below 2.2 R_Sun at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most of the jets display measureable swaying and bending of a few degrees in amplitude; in three jets the swaying is discernibly oscillatory with a period of order 1 hr. These characteristics suggest that the driver in these jets is a magnetic-untwisting wave that is basically a large-amplitude (i.e., nonlinear) torsional Alfvén wave that is put into the reconnected open field in the jet by interchange reconnection as the jet erupts. From the measured spinning and swaying, we estimate that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 R_Sun. We point out that the torsional waves observed in Type-II spicules might dissipate in the corona in the same way as the magnetic-untwisting waves in our big jets, and thereby power much of the coronal heating in coronal holes.

Based on the observed data by the Nobeyama Radio Observatory and the nonthermal gyrosynchrotron theory, the calculated magnetic field in a loop-like radio source of the 2001 October 23 flare attenuates from hundreds to tens of Gauss, except in the region with very weak magnetic fields. Meanwhile, the viewing angle between the magnetic field and line of sight has a similar attenuation from tens to around ten degrees, implying that the transverse magnetic component attenuates much faster than the longitudinal one. All of these results can be understood by the magnetic energy release process in solar flares. Moreover, the column density of nonthermal electrons decreases from 10⁹⁻¹⁰ to 10⁷⁻⁸ cm⁻² during the flare, except in the region with very weak magnetic fields, where its value is larger than that with strong magnetic fields due to the mirroring effect. The calculated error and harmonic number of gyrofrequency better suit the region with strong magnetic fields.

We studied the coronal mass ejection (CME) height at the onset of 59 metric type II radio bursts associated with major solar energetic particle (SEP) events, excluding ground level enhancements (GLEs), during solar cycles 23 and 24. We calculated CME heights using a simple flare-onset method used by Gopalswamy et al. to estimate CME heights at the metric type II onset for cycle 23 GLEs. We found the mean CME height for non-GLE events (1.72 R_☉) to be ∼12% greater than that (1.53 R_☉) for cycle 23 GLEs. The difference could be caused by more impulsive acceleration of the GLE-associated CMEs. For cycle 24 non-GLE events, we compared the CME heights obtained using the flare-onset method and the three-dimensional spherical-shock fitting method and found the correlation to be good (CC = 0.68). We found the mean CME height for cycle 23 non-GLE events (1.79 R_☉) to be greater than that for cycle 24 non-GLE events (1.58 R_☉), but statistical tests do not definitely reject the possibility of coincidence. We suggest that the lower formation height of the shocks during cycle 24 indicates a change in the Alfvén speed profile because solar magnetic fields are weaker and plasma density levels are closer to the surface than usual during cycle 24. We also found that complex type III bursts showing diminution of type III emission in the 7–14 MHz frequency range are more likely associated with events with a CME height at the type II onset above 2 R_☉, supporting suggestions that the CME/shock structure causes the feature.

A triplet of subordinate lines of Mg ii exists in the region around the h&k lines. In solar spectra these lines are seen mostly in absorption, but in some cases can become emission lines. The aim of this work is to study the formation of this triplet, and investigate any diagnostic value they can bring. Using 3D radiative magnetohydrodynamic simulations of quiet Sun and flaring flux emergence, we synthesize spectra and investigate how spectral features respond to the underlying atmosphere. We find that emission in the lines is rare and is typically caused by a steep temperature increase in the lower chromosphere (above 1500 K, with electron densities above 10¹⁷ m⁻³). In both simulations the lines are sensitive to temperature increases taking place at column masses ≳5 · 10⁻⁴ g cm⁻². Additional information can also be inferred from the peak-to-wing ratio and shape of the line profiles. Using observations from NASA's Interface Region Imaging Spectrograph we find both absorption and emission line profiles with similar shapes to the synthetic spectra, which suggests that these lines represent a useful diagnostic that complements the Mg ii h&k lines.

We present a sample of 27 gamma-ray bursts (GRBs) with detailed Swift light curves supplemented by late-time Chandra observations. To answer the missing jet-break problem in general, we develop a numerical-simulation-based model that can be directly fit to the data using Monte Carlo methods. Our numerical model takes into account all the factors that can shape a jet break: (i) lateral expansion, (ii) edge effects, and (iii) off-axis effects. Our results provide improved fits to the light curves and constraints on physical parameters. More importantly, our results suggest that off-axis effects are important and must be included in interpretations of GRB jet breaks.

The CHemical Abundances of Spirals (CHAOS) project leverages the combined power of the Large Binocular Telescope (LBT) with the broad spectral range and sensitivity of the Multi Object Double Spectrograph (MODS) to measure "direct" abundances (based on observations of the temperature-sensitive auroral lines) in large samples of H ii regions in spiral galaxies. We present LBT MODS observations of 62 H ii regions in the nearby spiral galaxy NGC 628, with an unprecedentedly large number of auroral lines measurements (18 [O iii] λ4363, 29 [N ii] λ5755, 40 [S iii]λ6312, and 40 [O ii] λλ7320, 7330 detections) in 45 H ii regions. Comparing derived temperatures from multiple auroral line measurements, we find: (1) a strong correlation between temperatures based on [S iii] λ6312 and [N ii] λ5755; and (2) large discrepancies for some temperatures based on [O ii] λλ7320, 7330 and [O iii] λ4363. Both of these trends are consistent with other observations in the literature, yet, given the widespread use and acceptance of [O iii] λ4363 as a temperature determinant, the magnitude of the T[O iii] discrepancies still came as a surprise. Based on these results, we conduct a uniform abundance analysis prioritizing the temperatures derived from [S iii] λ6312 and [N ii] λ5755, and report the gas-phase abundance gradients for NGC 628. Relative abundances of S/O, Ne/O, and Ar/O are constant across the galaxy, consistent with no systematic change in the upper IMF over the sampled range in metallicity. These alpha-element ratios, along with N/O, all show small dispersions (σ ∼ 0.1 dex) over 70% of the azimuthally averaged radius. We interpret these results as an indication that, at a given radius, the interstellar medium in NGC 628 is chemically well-mixed. Unlike the gradients in the nearly temperature-independent relative abundances, O/H abundances have a larger intrinsic dispersion of ∼0.165 dex. We posit that this dispersion represents an upper limit to the true dispersion in O/H at a given radius and that some of that dispersion is due to systematic uncertainties arising from temperature measurements.

We present Atacama Large Millimeter Array (ALMA) Cycle-0 observations of the CO J = 6–5 line in the advanced galaxy merger Arp 220. This line traces warm molecular gas, which dominates the total CO luminosity. The CO emission from the two nuclei is well resolved by the $0\buildrel{\prime\prime}\over{.} 39\times 0\buildrel{\prime\prime}\over{.} 22$ beam and the exceptional sensitivity and spatial/spectral resolution reveal new complex features in the morphology and kinematics of the warm gas. The line profiles are asymmetric between the red and blue sides of the nuclear disks and the peak of the line emission is offset from the peak of the continuum emission in both nuclei by about 100 pc in the same direction. CO self-absorption is detected at the centers of both nuclei but it is much deeper in the eastern nucleus. We also clearly detect strong, highly redshifted CO absorption located near the southwest side of each nucleus. For the eastern nucleus, we reproduce the major line profile features with a simple kinematic model of a highly turbulent, rotating disk with a substantial line center optical depth and a large gradient in the excitation temperature. The red/blue asymmetries and line-to-continuum offset are likely produced by absorption of the blue (SW) sides of the two nuclei by blueshifted, foreground molecular gas; the mass of the absorber is comparable to the nuclear warm gas mass (∼${{10}^{8}}$${{M}_{\odot }}$). We measure an unusually high ${{L}_{{\rm CO}}}/{{L}_{{\rm FIR}}}$ ratio in the eastern nucleus, suggesting there is an additional energy source, such as mechanical energy from shocks, present in this nucleus.

We present scaling relations between the integrated Sunyaev–Zel'dovich effect (SZE) signal, ${{Y}_{{\rm SZ}}}$, its X-ray analogue, ${{Y}_{{\rm X}}}$ ≡ ${{M}_{{\rm gas}}}$${{T}_{{\rm X}}}$, and total mass, ${{M}_{{\rm tot}}}$, for the 45 galaxy clusters in the Bolocam X-ray SZ (BOXSZ) sample. All parameters are integrated within ${{r}_{2500}}$. ${{Y}_{2500}}$ values are measured using SZE data collected with Bolocam, operating at 140 GHz at the Caltech Submillimeter Observatory. The temperature, ${{T}_{{\rm X}}}$, and mass, ${{M}_{{\rm gas},2500}}$, of the intracluster medium are determined using X-ray data collected with Chandra, and ${{M}_{{\rm tot}}}$ is derived from ${{M}_{{\rm gas}}}$ assuming a constant gas mass fraction. Our analysis accounts for several potential sources of bias, including selection effects, contamination from radio point sources, and the loss of SZE signal due to noise filtering and beam-smoothing effects. We measure the ${{Y}_{2500}}$–${{Y}_{{\rm X}}}$ scaling to have a power-law index of 0.84 ± 0.07, and a fractional intrinsic scatter in ${{Y}_{2500}}$ of $(21\pm 7)\%$ at fixed ${{Y}_{{\rm X}}}$, both of which are consistent with previous analyses. We also measure the scaling between ${{Y}_{2500}}$ and ${{M}_{2500}}$, finding a power-law index of 1.06 ± 0.12 and a fractional intrinsic scatter in ${{Y}_{2500}}$ at fixed mass of $(25\pm 9)\%$. While recent SZE scaling relations using X-ray mass proxies have found power-law indices consistent with the self-similar prediction of 5/3, our measurement stands apart by differing from the self-similar prediction by approximately 5σ. Given the good agreement between the measured ${{Y}_{2500}}$–${{Y}_{{\rm X}}}$ scalings, much of this discrepancy appears to be caused by differences in the calibration of the X-ray mass proxies adopted for each particular analysis.

We report the first direct and robust measurement of the faint-end slope of the Lyα emitter (LAE) luminosity function (LF) at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan-Baade were targeted at higher resolution to distinguish high-redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems have flux $F\lt 2.0\times {{10}^{-17}}$ ergs s⁻¹ cm⁻², making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE LF. We find 13 LAEs as compared to 29 foreground galaxies, in very good agreement with the modeled foreground counts predicted in Dressler et al. that had been used to estimate a faint-end slope of α = −2.0 for the LAE LF. A 32% LAE fraction, LAE/(LAE+foreground) within the flux interval $F=2-20$$\;\times \;{{10}^{-18}}$ ergs s⁻¹ cm⁻² constrains the faint end slope of the LF to $-2.35\lt \alpha \lt -1.95$ (1σ). We show how this steep LF should provide, to the limit of our observations, ${{M}_{{\rm UV}}}\;\sim$ −16, more than 20% of the flux necessary to maintain ionization at z = 5.7, with a factor of 10 extrapolation in flux reaching more than 50%. This is in addition to the comparable contribution by brighter Lyman Break Galaxies ${{M}_{{\rm UV}}}\;\lesssim$ −18. We suggest that this bodes well for a sufficient supply of Lyman continuum photons by similar, low-mass star-forming galaxies within the reionization epoch at $z\approx 7$, only 250 Myr earlier.

The events recorded by ARGO-YBJ in more than five years of data collection have been analyzed to determine the diffuse gamma-ray emission in the Galactic plane at Galactic longitudes 25° < l < 100° and Galactic latitudes $|b|\lt 5{}^\circ$. The energy range covered by this analysis, from ∼350 GeV to ∼2 TeV, allows the connection of the region explored by Fermi with the multi-TeV measurements carried out by Milagro. Our analysis has been focused on two selected regions of the Galactic plane, i.e., 40° < l < 100° and 65° < l < 85° (the Cygnus region), where Milagro observed an excess with respect to the predictions of current models. Great care has been taken in order to mask the most intense gamma-ray sources, including the TeV counterpart of the Cygnus cocoon recently identified by ARGO-YBJ, and to remove residual contributions. The ARGO-YBJ results do not show any excess at sub-TeV energies corresponding to the excess found by Milagro, and are consistent with the predictions of the Fermi model for the diffuse Galactic emission. From the measured energy distribution we derive spectral indices and the differential flux at 1 TeV of the diffuse gamma-ray emission in the sky regions investigated.

Red Supergiants (RSGs) are cool (∼4000 K), highly luminous stars ($L\sim {{10}^{5}}$L$_{\odot }$), and are among the brightest near-IR sources in star-forming galaxies. This makes them powerful probes of the properties of their host galaxies, such as kinematics and chemical abundances. We have developed a technique whereby metallicities of RSGs may be extracted from a narrow spectral window around 1 μm from only moderate resolution data. The method is therefore extremely efficient, allowing stars at large distances to be studied, and so has tremendous potential for extragalactic abundance work. Here, we present an abundance study of the Large and Small Magellanic Clouds (LMC and SMC respectively) using samples of 9–10 RSGs in each. We find average abundances for the two galaxies of ${{[Z]}_{{\rm LMC}}}=-0.37\pm 0.14$ and ${{[Z]}_{{\rm SMC}}}=-0.53\pm 0.16$ (with respect to a solar metallicity of ${{Z}_{\odot }}=0.012$). These values are consistent with other studies of young stars in these galaxies, and though our result for the SMC may appear high it is consistent with recent studies of hot stars which find 0.5–0.8 dex below solar. Our best-fit temperatures are on the whole consistent with those from fits to the optical-infrared spectral energy distributions, which is remarkable considering the narrow spectral range being studied. Combined with our recent study of RSGs in the Galactic cluster Per OB1, these results indicate that this technique performs well over a range of metallicities, paving the way for forthcoming studies of more distant galaxies beyond the Local Group.

We have completed two years of photometric and spectroscopic monitoring of a large number of active galactic nuclei (AGNs) with very high accretion rates. In this paper, we report on the result of the second phase of the campaign, during 2013–2014, and the measurements of five new Hβ time lags out of eight monitored AGNs. All five objects were identified as super-Eddington accreting massive black holes (SEAMBHs). The highest measured accretion rates for the objects in this campaign are $\mathscr{\dot{M}}\ \ {\mkern 1mu} \gtrsim 200$, where $\mathscr{\dot{M}}\ \ {\mkern 1mu} ={{\dot{M}}_{\bullet }}/{{L}_{{\rm Edd}}}{{c}^{-2}}$, ${{\dot{M}}_{\bullet }}$ is the mass accretion rates, ${{L}_{{\rm Edd}}}$ is the Eddington luminosity and c is the speed of light. We find that the Hβ time lags in SEAMBHs are significantly shorter than those measured in sub-Eddington AGNs, and the deviations increase with increasing accretion rates. Thus, the relationship between broad-line region size (${{R}_{_{{\rm H}\beta }}}$) and optical luminosity at 5100 Å, ${{R}_{_{{\rm H}\beta }}}-{{L}_{5100}}$, requires accretion rate as an additional parameter. We propose that much of the effect may be due to the strong anisotropy of the emitted slim-disk radiation. Scaling ${{R}_{_{{\rm H}\beta }}}$ by the gravitational radius of the black hole (BH), we define a new radius–mass parameter ($Y$) and show that it saturates at a critical accretion rate of $\mathscr{\dot{M}}\ \ {\mkern 1mu} {{}_{c}}=6\sim 30$, indicating a transition from thin to slim accretion disk and a saturated luminosity of the slim disks. The parameter $Y$ is a very useful probe for understanding the various types of accretion onto massive BHs. We briefly comment on implications to the general population of super-Eddington AGNs in the universe and applications to cosmology.

The intermediate phases of planet formation are not directly observable due to lack of emission from planetesimals. Planet formation is, however, a dynamically active process resulting in collisions between the evolving planetesimals and the production of dust. Thus, indirect observation of planet formation may indeed be possible in the near future. In this paper we present synthetic observations based on numerical N-body simulations of the intermediate phase of planet formation including a state-of-the-art collision model, EDACM, which allows multiple collision outcomes, such as accretion, erosion, and bouncing events. We show that the formation of planetary embryos may be indirectly observable by a fully functioning ALMA telescope if the surface area involved in planetesimal evolution is sufficiently large and/or the amount of dust produced in the collisions is sufficiently high in mass.

In light of the latest IceCube data, we discuss the implications of the cosmic ray (CR) energy input from hypernovae (HNe) and supernovae (SNe) into the universe, and their propagation in the hosting galaxies and galaxy clusters or groups. The magnetic confinement of CRs in these environments may lead to efficient neutrino production via pp collisions, resulting in a diffuse neutrino spectrum extending from PeV down to 10 TeV energies, with a spectrum and flux level compatible with that recently reported by IceCube. If the diffuse 10 TeV neutrino background largely comes from such CR reservoirs, the corresponding diffuse γ-ray background should be compatible with the recent Fermi data. In this scenario, the CR energy input from HNe should be dominant over that of SNe, implying that the starburst scenario does not work if the SN energy budget is a factor of two larger than the HN energy budget. Thus, this strong case scenario can be supported or ruled out in the near future.

We report observations of four sub-damped Lyα (sub-DLA) quasar absorbers at $z\lt 0.5$ obtained with the Hubble Space Telescope Cosmic Origins Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S, Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at $z\lt 0.5$ and improved constraints on sub-DLA chemical evolution. All four of our sub-DLAs are consistent with near-solar or super-solar metallicities and relatively modest ionization corrections; observations of more lines and detailed modeling will help to verify this. Combining our data with measurements from the literature, we confirm previous suggestions that the N(H i)-weighted mean metallicity of sub-DLAs exceeds that of DLAs at all redshifts studied, even after making ionization corrections for sub-DLAs. The absorber toward PHL 1598 shows significant dust depletion. The absorbers toward PHL 1226 and PKS 0439-433 show the S/P ratio consistent with solar, i.e., they lack a profound odd–even effect. The absorber toward Q0439-433 shows super-solar Mn/Fe. For several sub-DLAs at $z\lt 0.5$, [N/S] is below the level expected for secondary N production, suggesting a delay in the release of the secondary N or a tertiary N production mechanism. We constrain the electron density using Si ii* and C ii* absorption. We also report different metallicity versus ${\Delta }{{V}_{90}}$ relations for sub-DLAs and DLAs. For two sub-DLAs with detections of emission lines from the underlying galaxies, our measurements of the absorption-line metallicities are consistent with the emission-line metallicities, suggesting that metallicity gradients are not significant in these galaxies.

We present CARMA 30 GHz Sunyaev–Zel'dovich (SZ) observations of five high-redshift ($z\gtrsim 1$), infrared-selected galaxy clusters discovered as part of the all-sky Massive and Distant Clusters of WISE Survey (MaDCoWS). The SZ decrements measured toward these clusters demonstrate that the MaDCoWS selection is discovering evolved, massive galaxy clusters with hot intracluster gas. Using the SZ scaling relation calibrated with South Pole Telescope clusters at similar masses and redshifts, we find these MaDCoWS clusters have masses in the range ${{M}_{200}}\approx 2-6\times {{10}^{14}}$${{M}_{\odot }}$. Three of these are among the most massive clusters found to date at $z\gtrsim 1$, demonstrating that MaDCoWS is sensitive to the most massive clusters to at least z = 1.3. The added depth of the AllWISE data release will allow all-sky infrared cluster detection to z ≈ 1.5 and beyond.

The shock interaction and evolution of nova ejecta with wind from a red giant (RG) star in a symbiotic binary system are investigated via three-dimensional hydrodynamics simulations. We specifically model the 2010 March outburst of the symbiotic recurrent nova V407 Cygni from its quiescent phase to its eruption phase. The circumstellar density enhancement due to wind–white-dwarf interaction is studied in detail. It is found that the density-enhancement efficiency depends on the ratio of the orbital speed to the RG wind speed. Unlike another recurrent nova, RS Ophiuchi, we do not observe a strong disk-like density enhancement, but instead observe an aspherical density distribution with ∼20% higher density in the equatorial plane than at the poles. To model the 2010 outburst, we consider several physical parameters, including the RG mass-loss rate, nova eruption energy, and ejecta mass. A detailed study of the shock interaction and evolution reveals that the interaction of shocks with the RG wind generates strong Rayleigh–Taylor instabilities. In addition, the presence of the companion and circumstellar density enhancement greatly alter the shock evolution during the nova phase. Depending on the model, the ejecta speed after sweeping out most of the circumstellar medium decreases to ∼100–300 km s⁻¹, which is consistent with the observed extended redward emission in [N ii] lines in 2011 April.

We show that turbulence in core collapse supernovae (CCSNe) which has been shown recently to ease shock revival might also lead to the formation of intermittent thick accretion disks, or accretion belts, around the newly born neutron star (NS). The accretion morphology is such that two low density funnels are formed along the polar directions. The disks then are likely to launch jets with a varying axis direction, i.e., jittering jets, through the two opposite funnels. The energy contribution of jets in this jittering-jets mechanism might result in an explosion energy of ${{E}_{{\rm exp} }}\;\gtrsim \;{{10}^{51}}\;{\rm erg}$, even without reviving the stalled shock. We strengthen the jittering-jets mechanism as a possible explosion mechanism of CCSNe.

We present here the first spectroscopic and photometric analysis of the double-lined eclipsing binary containing the classical, first-overtone (FO) Cepheid OGLE-LMC-CEP-2532 (MACHO 81.8997.87). The system has an orbital period of 800 days and the Cepheid is pulsating with a period of 2.035 days. Using spectroscopic data from three high-class telescopes and photometry from three surveys spanning 7500 days, we are able to derive the dynamical masses for both stars with an accuracy better than 3%. This makes the Cepheid in this system one of a few classical Cepheids with an accurate dynamical mass determination (${{M}_{1}}=3.90\pm 0.10\;{{M}_{\odot }}$). The companion is probably slightly less massive ($3.82\pm 0.10\;{{M}_{\odot }}$), but may have the same mass within errors (${{M}_{2}}/{{M}_{1}}=0.981\pm 0.015$). The system has an age of about 185 million years and the Cepheid is in a more advanced evolutionary stage. For the first time precise parameters are derived for both stars in this system. Due to the lack of the secondary eclipse for many years, not much was known about the Cepheid's companion. In our analysis, we used extra information from the pulsations and the orbital solution from the radial velocity curve. The best model predicts a grazing secondary eclipse shallower than 1 mmag, hence undetectable in the data, about 370 days after the primary eclipse. The dynamical mass obtained here is the most accurate known for a FO Cepheid and will contribute to the solution of the Cepheid mass discrepancy problem.

With the loss of a second reaction wheel, resulting in the inability to point continuously and stably at the same field of view, the NASA Kepler satellite recently entered a new mode of observation known as the K2 mission. The data from this redesigned mission present a specific challenge; the targets systematically drift in position on an ∼6 hr timescale, inducing a significant instrumental signal in the photometric time series—this greatly impacts the ability to detect planetary signals and perform asteroseismic analysis. Here we detail our version of a reduction pipeline for K2 target pixel data, which automatically defines masks for all targets in a given frame; extracts the target's flux and position time series; corrects the time series based on the apparent movement on the CCD (either in 1D or 2D), combined with the correction of instrumental and/or planetary signals via the Kepler Asteroseismic Science Operations Center (KASOC) filter, thus rendering the time series ready for asteroseismic analysis; computes power spectra for all targets; and identifies potential contaminations between targets. From a test of our pipeline on a sample of targets from the K2 campaign 0, the recovery of data for multiple targets increases the amount of potential light curves by a factor of $\geqslant 10$. Our pipeline could be applied to the upcoming TESS and PLATO 2.0 missions.

We investigate prestellar core formation and accretion based on three-dimensional hydrodynamic simulations. Our simulations represent local ∼1 pc regions within giant molecular clouds where a supersonic turbulent flow converges, triggering star formation in the post-shock layer. We include turbulence and self-gravity, applying sink particle techniques, and explore a range of inflow Mach numbers $\mathcal{M}=2-16$. Two sets of cores are identified and compared: t₁ cores are identified from a time snapshot in each simulation and represent dense structures in a single cloud map; t_coll cores are identified at their individual time of collapse and represent the initial mass reservoir for accretion. We find that cores and filaments form and evolve at the same time. At the stage of core collapse, there is a well-defined, converged characteristic mass for isothermal fragmentation that is comparable to the critical Bonnor–Ebert mass at the post-shock pressure. The core mass functions (CMFs) of t_coll cores show a deficit of high-mass cores ($\gtrsim 7\;{{M}_{\odot }}$) compared to the observed stellar initial mass function (IMF). However, the CMFs of t₁ cores are similar to the observed CMFs and include many low-mass cores that are gravitationally stable. The difference between t₁ cores and t_coll cores suggests that the full sample from observed CMFs may not evolve into protostars. Individual sink particles accrete at a roughly constant rate throughout the simulations, gaining one core mass per freefall time even after the initial mass reservoir is accreted. High-mass sinks gain proportionally more mass at later times than low-mass sinks. There are outbursts in accretion rates, resulting from clumpy density structures falling into the sinks.

This paper presents a theory for the asymptotically steady-state solar wind electron velocity distribution function (VDF) in a local equilibrium with plasma wave turbulence. By treating the local solar wind electron VDF as a superposition of three populations—the low-energy Maxwellian core electrons with an energy range of tens of eV, the intermediate $\sim {{10}^{2}}$–10³ eV energy-range halo electrons, and the high $\sim {{10}^{3}}$–10⁵ eV energy-range superhalo electrons—the present paper puts forth a model in which the halo electrons are in dynamical steady state with the pervasive whistler fluctuations, while the superhalo electrons maintain dynamical steady-state equilibrium with the Langmuir fluctuations, known as the quasi-thermal noise. Customary models of the solar wind electrons include only the Maxwellian core and the halo (plus highly field-aligned strahl). While the present paper does not consider the strahl population in the discussion, the highly energetic superhalo component, which is observed to be present in all solar conditions, is explicitly taken into account as part of the total solar wind electron model. Comparisons with STEREO and WIND spacecraft observations are also made.

Three-dimensional numerical hybrid simulations with particle protons and quasi-neutralizing, fluid electrons are conducted for a freely decaying turbulence. The main results are obtained from a series of runs as a function of the initial total rms fluctuation amplitude. In the turbulent phase and at a corresponding nonlinear time dependent on the amplitude, the scaling of the proton perpendicular heating rate is examined as a function of the spectral value of the electron bulk perpendicular speed integrated in wavenumbers about the inverse thermal proton gyroradius. The perpendicular direction is relative to the background magnetic field. The obtained spectral value is normalized to the proton thermal speed and ranges from 0.06 to 0.16. The scaling of the perpendicular heating rate with this spectral value is fitted with a power law, which has an index of −3.3 ± 0.2. The fit is consistent with the scaling of the total heating rate as a function of total rms amplitude, which has an index of −3.06 ± 0.12. The power-law index is near the turbulent hydrodynamic-like prediction for the energy cascade rate as a function of amplitude. The heating rate, then, obeys a power law with amplitude or spectral value regardless of whether that quantity is evaluated at large scales or at the proton gyroradius scales.

A scenario based on electron cyclotron maser (ECM) emission is proposed for the fine structures of solar radio emission. It is suggested that under certain conditions modulation of the ratio between the plasma frequency and electron gyro frequency by ultra-low-frequency waves, which is a key parameter for excitation of ECM instability, may lead to the intermittent emission of radio waves. As an example, the explanation for the observed fine-structure components in the solar Type IIIb bursts is discussed in detail. Three primary issues of Type IIIb bursts are addressed: (1) the physical mechanism that results in intermittent emission elements that form a chain in the dynamic spectrum of Type IIIb bursts, (2) the cause of split pairs (or double stria) and triple stria, and (3) why only IIIb–III bursts are observed in the events of fundamental harmonic pair emission whereas IIIb–IIIb or III–IIIb bursts are very rarely observed.

We present an analysis of the physical conditions in an extreme molecular cloud in the Antennae merging galaxies. This cloud has properties consistant with those required to form a globular cluster. We have obtained ALMA CO and 870 μm observations of the Antennae galaxy system with ∼05 resolution. This cloud stands out in the data with a radius of ≲24 pc and mass of >5 × 10⁶M_⊙. The cloud appears capable of forming a globular cluster, but the lack of associated thermal radio emission indicates that star formation has not yet altered the environment. The lack of thermal radio emission places the cloud in an early stage of evolution, which we expect to be short-lived (≲1 Myr) and thus rare. Given its mass and kinetic energy, for the cloud to be confined (as its appearance strongly suggests) it must be subject to an external pressure of P/k_B ≳ 10⁸ K cm⁻³–10,000 times higher than typical interstellar pressure. This would support theories that high pressures are required to form globular clusters and may explain why extreme environments like the Antennae are preferred environments for generating such objects. Given the cloud temperature of ∼25 K, the internal pressure must be dominated by non-thermal processes, most likely turbulence. We expect the molecular cloud to collapse and begin star formation in ≲1 Myr.

An increasing body of data reveals a one-to-one linear correlation between galaxy halo mass and the total mass in its globular cluster (GC) population, ${{M}_{{\rm GCS}}}\sim M_{h}^{1.03\pm 0.03}$, valid over five orders of magnitude. In this paper we explore the nature of this correlation for galaxies of different morphological types and for the subpopulations of metal-poor (blue) and metal-rich (red) GCs. For the subpopulations of different metallicity, we find ${{M}_{{\rm GCS}}}({\rm blue})\sim M_{h}^{0.96\pm 0.03}$ and ${{M}_{{\rm GCS}}}({\rm red})\sim M_{h}^{1.21\pm 0.03}$ with similar scatter. The numerical values of these exponents can be derived from the detailed behavior of the red and blue GC fractions with galaxy mass and provide a self-consistent set of relations. In addition, all morphological types (E, S0, S/Irr) follow the same relation, but with a second-order trend for spiral galaxies to have a slightly higher fraction of metal-rich GCs for a given mass. These results suggest that the amount of gas available for GC formation at high redshift was in nearly direct proportion to the dark matter halo potential, in strong contrast to the markedly nonlinear behavior of total stellar mass versus halo mass. Of the few available theoretical treatments that directly discuss the formation of GCs in a hierarchical-merging framework, we find that the model of Kravtsov & Gnedin best matches these observations. They find that the blue, metal-poor GCs formed in small halos at $z\gt 3$ and did so in nearly direct proportion to halo mass. Similar models addressing the formation rate of the red, more metal-rich GCs in the same detail and continuing to lower redshift are still needed for a comprehensive picture.

We present an analysis of the X-ray spectrum and long-term variability of the nearby dwarf starburst galaxy Henize 2–10. Recent observations suggest that this galaxy hosts an actively accreting black hole (BH) with mass ∼10⁶${{M}_{\odot }}$. The presence of an active galactic nucleus (AGN) in a low-mass starburst galaxy marks a new environment for AGNs, with implications for the processes by which "seed" BHs may form in the early universe. In this paper, we analyze four epochs of X-ray observations of Henize 2–10, to characterize the long-term behavior of its hard nuclear emission. We analyze observations with Chandra from 2001 and XMM-Newton from 2004 and 2011, as well as an earlier, less sensitive observation with ASCA from 1997. Based on a detailed analysis of the source and background, we find that the hard (2–10 keV) flux of the putative AGN has decreased by approximately an order of magnitude between the 2001 Chandra observation and exposures with XMM-Newton in 2004 and 2011. The observed variability confirms that the emission is due to a single source. It is unlikely that the variable flux is due to a supernova or ultraluminous X-ray source, based on the observed long-term behavior of the X-ray and radio emission, while the observed X-ray variability is consistent with the behavior of well-studied AGNs.

We present $^{13}{\rm CO}$ and ${{{\rm C}}^{18}}{\rm O}$ (1-0), (2-1), and (3-2) maps toward the core-forming Perseus B1-E clump using observations from the James Clerk Maxwell Telescope, the Submillimeter Telescope of the Arizona Radio Observatory, and the IRAM 30 m telescope. We find that the $^{13}{\rm CO}$ and ${{{\rm C}}^{18}}{\rm O}$ line emission both have very complex velocity structures, indicative of multiple velocity components within the ambient gas. The (1–0) transitions reveal a radial velocity gradient across B1-E of $\sim 1\;{\rm km}\;{{{\rm s}}^{-1}}\;{\rm p}{{{\rm c}}^{-1}}$ that increases from northwest to southeast, whereas the majority of the Perseus cloud has a radial velocity gradient increasing from southwest to northeast. In contrast, we see no evidence of a velocity gradient associated with the denser Herschel-identified substructures in B1-E. Additionally, the denser substructures have much lower systemic motions than the ambient clump material, which indicates that they are likely decoupled from the large-scale gas. Nevertheless, these substructures themselves have broad line widths (∼0.4 ${\rm km}\;{{{\rm s}}^{-1}}$) similar to that of the ${{{\rm C}}^{18}}{\rm O}$ gas in the clump, which suggests they inherited their kinematic properties from the larger-scale, moderately dense gas. Finally, we find evidence of ${{{\rm C}}^{18}}{\rm O}$ depletion only toward one substructure, B1-E2, which is also the only object with narrow (transonic) line widths. We suggest that as prestellar cores form, their chemical and kinematic properties are linked in evolution, such that these objects must first dissipate their turbulence before they deplete in CO.

We present an estimate of the mass of the supermassive black hole (SMBH) in the nearby type-1 Seyfert galaxy NGC 1097 using Atacamma Large Millimeter/submillimeter Array (ALMA) observations of dense gas kinematics. Dense molecular gas dynamics are traced with ${\rm HCN}(J=1-0)$ and ${\rm HC}{{{\rm O}}^{+}}(J=1-0)$ emission lines. Assuming a host galaxy inclination of $46{}^\circ$, we derive an SMBH mass, ${{M}_{{\rm BH}}}=1.40_{-0.32}^{+0.27}\times {{10}^{8\,}}{{M}_{\odot }}$, and an I-band mass to light ratio to be $5.14_{-0.04}^{+0.03}$, using ${\rm HCN}(J=1-0)$. The estimated parameters are consistent between the two emission lines. The measured SMBH mass is in good agreement with the SMBH mass and bulge velocity dispersion relationship. Our result showcases ALMA's potential for deriving accurate SMBH masses, especially for nearby late-type galaxies. Larger samples and accurate SMBH masses will further elucidate the relationship between the black hole (BH) and host galaxy properties and constrain the coevolutionary growth of galaxies and BHs.

We have conducted a ¹³CO survey of a sample of 128 infrared color-selected intermediate-mass star-forming region (IM SFR) candidates. We utilized the Onsala 20 m telescope to observe ¹³CO (1–0) toward 67 northern IM SFRs, used the 12 m Atacama Pathfinder Experiment telescope to observe ¹³CO (2–1) toward 22 southern IM SFRs, and incorporated an additional 39 sources from the Boston University Five College Radio Astronomy Observatory Galactic Ring Survey which observed ¹³CO (1–0). We detect ¹³CO (1–0) in 58 of the 67 northern sources and ¹³CO (2–1) in 20 of the 22 southern sources. The mean molecular column densities and ¹³CO linewidths in the inner Galaxy are higher by factors of 3.4 and 1.5, respectively, than the outer Galaxy. We attribute this difference to molecular clouds in the inner Galaxy being more massive and hosting star forming regions with higher luminosities on average than the outer Galaxy. IM SFRs have mean a molecular column density of 7.89 × 10²¹ cm⁻², a factor of 3.1 lower than that for a sample of high-mass regions, and have a mean ¹³CO linewidth of 1.84 km s⁻¹, a factor of 1.5 lower than that for high-mass regions. We demonstrate a correlation between ¹³CO linewidth and infrared luminosity as well as between molecular column density and infrared luminosity for the entire sample of intermediate-mass and high-mass regions. IM SFRs appear to form in distinctly lower-density environments with mean linewidths and beam-averaged column densities a factor of several lower than high-mass star-forming regions.

We study the interaction between the atmospheres of Venus-like, non-magnetized exoplanets orbiting an M-dwarf star, and the stellar wind using a multi-species MHD model. We focus our investigation on the effect of enhanced stellar wind and enhanced EUV flux as the planetary distance from the star decreases. Our simulations reveal different topologies of the planetary space environment for sub- and super-Alfvénic stellar wind conditions, which could lead to dynamic energy deposition into the atmosphere during the transition along the planetary orbit. We find that the stellar wind penetration for non-magnetized planets is very deep, up to a few hundreds of kilometers. We estimate a lower limit for the atmospheric mass-loss rate and find that it is insignificant over the lifetime of the planet. However, we predict that when accounting for atmospheric ion acceleration, a significant amount of the planetary atmosphere could be eroded over the course of a billion years.

We investigate pathways for the formation of icy super-Earth mass planets orbiting at 125–250 AU around a 1 ${{M}_{\odot }}$ star. An extensive suite of coagulation calculations demonstrates that swarms of 1 cm–10 m planetesimals can form super-Earth mass planets on timescales of 1–3 Gyr. Collisional damping of 10⁻²−10² cm particles during oligarchic growth is a highlight of these simulations. In some situations, damping initiates a second runaway growth phase where 1000–3000 km protoplanets grow to super-Earth sizes. Our results establish the initial conditions and physical processes required for in situ formation of super-Earth planets at large distances from the host star. For nearby dusty disks in HD 107146, HD 202628, and HD 207129, ongoing super-Earth formation at 80–150 AU could produce gaps and other structures in the debris. In the solar system, forming a putative planet X at $a\lesssim 300$ AU ($a\gtrsim 1000$ AU) requires a modest (very massive) protosolar nebula.

Understanding the outskirts of galaxy clusters at the virial radius (R₂₀₀) and beyond is critical for an accurate determination of cluster masses, structure growth, and to ensure unbiased cosmological parameter estimates from cluster surveys. This problem has drawn renewed interest due to recent determinations of gas mass fractions beyond R₂₀₀, which appear to be considerably larger than the cosmic mean. Here, we use a large suite of cosmological hydrodynamical simulations to study the inhomogeneity of the intra-cluster medium and employ different variants of simulated physics, including radiative gas physics and thermal feedback by active galactic nuclei. We find that density and pressure clumping closely trace each other as a function of radius, but the bias on density remains on average $\lt 20\%$ within R₂₀₀. At larger radii, clumping increases steeply due to the continuous infall of coherent structures that have not yet passed the accretion shock. Density and pressure clumping increase with cluster mass and redshift, which probes on average dynamically younger objects that are still in the process of assembling. The angular power spectra of gas density and pressure show that the clumping signal is dominated by large-scale cosmic filaments that reach from the cosmic web into the clusters, signaling the presence of gravitationally driven "super clumping." While the prolateness of the gravitational halo potential implies an approximate radial correlation of these gaseous large-scale structures, gas density and pressure lose coherence on small scales across different radii due to dissipative gas physics. In contrast, the angular power spectrum of dark matter shows an almost uniform size distribution due to unimpeded subhalos. We provide a synopsis of the radial dependence of the clusters' non-equilibrium measures (kinetic pressure support, ellipticity, and clumping) that all increase sharply beyond R₂₀₀.

Gamma-ray bursts (GRBs), by virtue of their high luminosities, can be detected up to very high redshifts and therefore can be excellent probes of the early universe. This task is hampered by the fact that most of their characteristics have a broad range, so we first need to obtain an accurate description of the distribution of these characteristics and, especially, their cosmological evolution. We use a sample of about 200 Swift long GRBs with known redshifts to determine the evolution of the luminosity, formation rate, and the general shape of the luminosity function (LF). In contrast to most other forward-fitting methods of treating this problem, we use the Efron–Petrosian methods, which allow a non-parametric determination of the above quantities. We find a relatively strong luminosity evolution, an LF that can be fitted to a broken power law, and an unusually high formation rate at low redshifts, a rate more than one order of magnitude higher than the star formation rate (SFR). On the other hand, our results seem to agree with the almost constant SFR in redshifts 1–3 and the decline above this redshift.

Weak lensing causes spatially coherent fluctuations in the flux of Type Ia supernovae (SNe Ia). This lensing magnification allows for weak lensing measurement independent of cosmic shear. It is free of the shape measurement errors associated with cosmic shear and can therefore be used to diagnose and calibrate multiplicative error. Although this lensing magnification is difficult to accurately measure in auto correlation, its cross correlation with cosmic shear and galaxy distribution in an overlapping area can be measured to a significantly higher accuracy. Therefore, these cross correlations can put useful constraints on multiplicative error, and the obtained constraint is free of cosmic variance in the weak lensing field. We present two methods implementing this idea and estimate their performances. We find that, with ∼1 million SNe Ia that can be achieved with the proposed D2k survey with the LSST telescope, a multiplicative error of ∼0.5% for source galaxies at ${{z}_{s}}\sim 1$ can be detected and a larger multiplicative error can be corrected to the level of 0.5%. It is therefore a promising approach to control the multiplicative error to the sub-percent level required for stage IV projects. The combination of the two methods even has the potential to diagnose and calibrate galaxy intrinsic alignment, which is another major systematic error in cosmic shear cosmology.

Lyα photons scattered by neutral hydrogen atoms in the circumgalactic media or produced in the halos of star-forming galaxies are expected to lead to extended Lyα emission around galaxies. Such low surface brightness Lyα halos (LAHs) have been detected by stacking Lyα images of high-redshift star-forming galaxies. We study the origin of LAHs by performing radiative transfer modeling of nine z = 3.1 Lyα emitters (LAEs) in a high resolution hydrodynamic cosmological galaxy formation simulation. We develop a method of computing the mean Lyα surface brightness profile of each LAE by effectively integrating over many different observing directions. Without adjusting any parameters, our model yields an average Lyα surface brightness profile in remarkable agreement with observations. We find that observed LAHs cannot be accounted for solely by photons originating from the central LAE and scattered to large radii by hydrogen atoms in the circumgalactic gas. Instead, Lyα emission from regions in the outer halo is primarily responsible for producing the extended LAHs seen in observations, which potentially includes both star-forming and cooling radiation. With the limit on the star formation contribution set by the ultraviolet halo measurement, we find that cooling radiation can play an important role in forming the extended LAHs. We discuss the implications and caveats of such a picture.

Hubble Space Telescope (HST) spectra of the EUV, the optically thick emission from the innermost accretion flow onto the central supermassive black hole, indicate that radio loud quasars (RLQs) tend to be EUV weak compared to the radio-quiet quasars; yet the remainder of the optically thick thermal continuum is indistinguishable. The deficit of EUV emission in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. This article is an examination of the evidence for a distribution of magnetic flux tubes in the innermost accretion flow that results in magnetically arrested accretion (MAA) and creates the EUV deficit. These same flux tubes and possibly the interior magnetic flux that they encircle are the sources of the jet power as well. In the MAA scenario, islands of large-scale vertical magnetic flux perforate the innermost accretion flow of RLQs. The first prediction of the theory that is supported by the HST data is that the strength of the (large-scale poloidal magnetic fields) jets in the MAA region is regulated by the ram pressure of the accretion flow in the quasar environment. The second prediction that is supported by the HST data is that the rotating magnetic islands remove energy from the accretion flow as a Poynting flux dominated jet in proportion to the square of the fraction of the EUV emitting gas that is displaced by these islands.

We have identified a major global enhancement of star formation in the inner M31 disk that occurred between 2–4 Gyr ago, producing ∼60% of the stellar mass formed in the past 5 Gyr. The presence of this episode in the inner disk was discovered by modeling the optical resolved star color–magnitude diagrams of low extinction regions in the main disk of M31 (3 < R < 20 kpc) as part of the Panchromatic Hubble Andromeda Treasury. This measurement confirms and extends recent measurements of a widespread star formation enhancement of similar age in the outer disk, suggesting that this burst was both massive and global. Following the galaxy-wide burst, the star formation rate of M31 has significantly declined. We briefly discuss possible causes for these features of the M31 evolutionary history, including interactions with M32, M33, and/or a merger.

We combine Herschel observations for a total of 12 sources to construct the most uniform survey of HF and H₂O in our Galactic disk. Both molecules are detected in absorption along all sight lines. The high spectral resolution of the Heterodyne Instrument for the Far-infrared (HIFI) allows us to compare the HF and H₂O distributions in 47 diffuse cloud components sampling the disk. We find that the HF and H₂O velocity distributions follow each other almost perfectly and establish that HF and H₂O probe the same gas-phase volume. Our observations corroborate theoretical predictions that HF is a sensitive tracer of H₂ in diffuse clouds, down to molecular fractions of only a few percent. Using HF to trace H₂ in our sample, we find that the N(H₂O)-to-N(HF) ratio shows a narrow distribution with a median value of 1.51. Our results further suggest that H₂O might be used as a tracer of H₂—within a factor of 2.5—in the diffuse interstellar medium (ISM). We show that the measured factor of ∼2.5 variation around the median is driven by true local variations in the H₂O abundance relative to H₂ throughout the disk. The latter variability allows us to test our theoretical understanding of the chemistry of oxygen-bearing molecules in the diffuse gas. We show that both gas-phase and grain-surface chemistry are required to reproduce our H₂O observations. This survey thus confirms that grain surface reactions can play a significant role in the chemistry occurring in the diffuse ISM (${{n}_{{\rm H}}}$$\leqslant$ 1000 cm⁻³).

We investigate the interaction of differential rotation and a misaligned magnetic field. The incompressible magnetohydrodynamic equations are solved numerically for a free-decay problem. In the kinematic limit, differential rotation annihilates the non-axisymmetric field on a timescale proportional to the cube root of magnetic Reynolds number (Rm), as predicted by Rädler. Nonlinearly, the outcome depends upon the initial energy in the non-axisymmetric part of the field. Sufficiently weak fields approach axisymmetry as in the kinematic limit; some differential rotation survives across magnetic surfaces, at least on intermediate timescales. Stronger fields enforce uniform rotation and remain non-axisymmetric. The initial field strength that divides these two regimes does not follow the scaling $R{{m}^{-1/3}}$ predicted by quasi-kinematic arguments, perhaps because our Rm is never sufficiently large or because of reconnection. We discuss the possible relevance of these results to tidal synchronization and tidal heating of close binary stars, particularly double white dwarfs.

Despite the discovery of thousands of exoplanets, no exomoons have been detected so far. We test a recently developed method for exomoon search, the orbital sampling effect (OSE), using the full exoplanet photometry from the Kepler Space Telescope. The OSE is applied to phase-folded transits, for which we present a framework to detect false positives, and discuss four candidates which pass several of our tests. Using numerical simulations, we inject exomoon signals into real Kepler data and retrieve them, showing that under favorable conditions, exomoons can be found with Kepler and the OSE method. In addition, we super-stack a large sample of Kepler planets to search for the average exomoon OSE and the accompanying increase in noise, the scatter peak. We find a significant OSE-like signal, which might indicate the presence of moons, for planets with $35\;{\rm days}\lt P\lt 80\;{\rm days}$, having an average dip per planet of 6 ± 2 ppm, corresponding to a moon radius of $2120_{-370}^{+330}$ km for the average star radius of 1.24 ${{R}_{\odot }}$ in this sample.

The Fermi Gamma-ray Space Telescope has greatly expanded the number and energy window of observations of gamma-ray bursts (GRBs). However, the coarse localizations of tens to a hundred square degrees provided by the Fermi GRB Monitor instrument have posed a formidable obstacle to locating the bursts' host galaxies, measuring their redshifts, and tracking their panchromatic afterglows. We have built a target-of-opportunity mode for the intermediate Palomar Transient Factory in order to perform targeted searches for Fermi afterglows. Here, we present the results of one year of this program: 8 afterglow discoveries out of 35 searches. Two of the bursts with detected afterglows (GRBs 130702A and 140606B) were at low redshift (z = 0.145 and 0.384, respectively) and had spectroscopically confirmed broad-line Type Ic supernovae. We present our broadband follow-up including spectroscopy as well as X-ray, UV, optical, millimeter, and radio observations. We study possible selection effects in the context of the total Fermi and Swift GRB samples. We identify one new outlier on the Amati relation. We find that two bursts are consistent with a mildly relativistic shock breaking out from the progenitor star rather than the ultra-relativistic internal shock mechanism that powers standard cosmological bursts. Finally, in the context of the Zwicky Transient Facility, we discuss how we will continue to expand this effort to find optical counterparts of binary neutron star mergers that may soon be detected by Advanced LIGO and Virgo.

We investigate the plausibility of detecting X-ray emission from a stellar jet that impacts a dense molecular cloud, a scenario that may be typical for classical T Tauri stars with jets in dense star-forming complexes. We first model the impact of a jet against a dense cloud using two-dimensional axisymmetric hydrodynamic simulations, exploring different configurations of the ambient environment. Then, we compare our results with XMM-Newton observations of the Herbig–Haro object HH 248, where extended X-ray emission aligned with the optical knots is detected at the edge of the nearby IC 434 cloud. Our simulations show that a jet can produce plasma with temperatures up to 10⁷ K, consistent with production of X-ray emission, after impacting a dense cloud. We find that jets denser than the ambient medium but less dense than the cloud produce detectable X-ray emission only at impact with the cloud. From an exploration of the model parameter space, we constrain the physical conditions (jet density and velocity and cloud density) that reproduce the intrinsic luminosity and emission measure of the X-ray source possibly associated with HH 248 well. Thus, we suggest that the extended X-ray source close to HH 248 corresponds to a jet impacting a dense cloud.

A powerful method to measure the mass profile of a galaxy is through the velocities of tracer particles distributed through its halo. Transforming this kind of data accurately to a mass profile $M(r)$, however, is not a trivial problem. In particular, limited or incomplete data may substantially affect the analysis. In this paper we develop a Bayesian method to deal with incomplete data effectively; we have a hybrid-Gibbs sampler that treats the unknown velocity components of tracers as parameters in the model. We explore the effectiveness of our model using simulated data and then apply our method to the Milky Way (MW) using velocity and position data from globular clusters and dwarf galaxies. We find that, in general, missing velocity components have little effect on the total mass estimate. However, the results are quite sensitive to the outer cluster Pal 3. Using a basic Hernquist model with an isotropic velocity dispersion, we obtain credible regions for the cumulative mass profile $M(r)$ of the MW and provide estimates for the model parameters with 95% Bayesian credible intervals. The mass contained within 260 kpc is $1.37\times {{10}^{12}}$${{M}_{\odot }}$, with a 95% credible interval of $(1.27,1.51)\times {{10}^{12}}$${{M}_{\odot }}$. The Hernquist parameters for the total mass and scale radius are $1.55_{-0.13}^{+0.18}\times {{10}^{12}}$${{M}_{\odot }}$ and $16.9_{-4.1}^{+4.8}$ kpc, where the uncertainties span the 95% credible intervals. The code we developed for this work, Galactic Mass Estimator (GME), will be available as an open source package in the R Project for Statistical Computing.

The higher charge states found in slow (<400 km s⁻¹) solar wind streams compared to fast streams have supported the hypothesis that the slow wind originates in closed coronal loops and is released intermittently through reconnection. Here we examine whether a highly ionized slow wind can also form along steady and open magnetic field lines. We model the steady-state solar atmosphere using the Alfvén Wave Solar Model (AWSoM), a global MHD model driven by Alfvén waves, and apply an ionization code to calculate the charge state evolution along modeled open field lines. This constitutes the first charge state calculation covering all latitudes in a realistic magnetic field. The ratios ${{{\rm O}}^{+7}}/{{{\rm O}}^{+6}}$ and ${{{\rm C}}^{+6}}/{{{\rm C}}^{+5}}$ are compared to in situ Ulysses observations and are found to be higher in the slow wind, as observed; however, they are underpredicted in both wind types. The modeled ion fractions of S, Si, and Fe are used to calculate line-of-sight intensities, which are compared to Extreme-ultraviolet Imaging Spectrometer (EIS) observations above a coronal hole. The agreement is partial and suggests that all ionization rates are underpredicted. Assuming the presence of suprathermal electrons improved the agreement with both EIS and Ulysses observations; importantly, the trend of higher ionization in the slow wind was maintained. The results suggest that there can be a sub-class of slow wind that is steady and highly ionized. Further analysis shows that it originates from coronal hole boundaries (CHBs), where the modeled electron density and temperature are higher than inside the hole, leading to faster ionization. This property of CHBs is global and observationally supported by EUV tomography.

A localized perturbation of a magnetic flux tube produces wave trains that disperse as they propagate along the tube, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. We find that the propagating wave train undergoes stronger attenuation for longer axisymmetric (or shorter transverse) perturbations, while the internal to external density ratio has a smaller effect on the attenuation. Moreover, for parameter values typical of coronal loops axisymmetric (transverse) wave trains travel at a speed 0.75–1 (1.2) times the Alfvén speed of the magnetic tube. In both cases, the wave train passage at a fixed position of the magnetic tube gives rise to oscillations with periods of the order of seconds, with axisymmetric disturbances causing more oscillations than transverse ones. To test the detectability of propagating transverse or axisymmetric wave packets in magnetic tubes of the solar atmosphere (e.g., coronal loops, spicules, or prominence threads) a forward modeling of the perturbations must be carried out.

We report high-resolution near-infrared absorption spectroscopy of H₂, H₃⁺, and CO toward the young high mass object NGC 7538 IRS 1. The v = 1–0 H₂S(0) line and lines in the CO v = 2–0 band were detected; the v = 1–0 H₂S(1) line and the v = 1–0 H₃⁺ lines [R(1, 1)^l, R(1, 0), R(1, 1)^u] were not detected. The line of sight traverses two clouds, with temperatures 45 and 259 K and with roughly equal column densities of CO. Assuming that H₂ is at the same temperature as CO and that the two species are uniformly mixed, [H₂]/[CO] = 3600 ± 1200. NGC 7538 is the most distant object from the Galactic center for which [H₂]/[CO] has been directly measured using infrared absorption spectroscopy.

Stellar-mass black holes (BHs) surrounded by neutrino-dominated accretion flows (NDAFs) are plausible sources of power for gamma-ray bursts (GRBs) via neutrino emission and their annihilation. The progenitors of short-duration GRBs (SGRBs) are generally considered to be compact binary mergers. According to the simulation results, the disk mass of the NDAF is limited after merger events. We can estimate such disk masses using the current SGRB observational data and fireball model. The results show that the disk mass of a certain SGRB mainly depends on its output energy, jet opening angle, and central BH characteristics. Even for the extreme BH parameters, some SGRBs require massive disks, which approach or exceed the limits in simulations. We suggest that there may exist alternative MHD processes or mechanisms that increase the neutrino emission to produce SGRBs with reasonable BH parameters and disk masses.

We present a model describing the evolution of Fanaroff–Riley type I and II radio active galactic nuclei (AGNs) and the transition between these classes. We quantify galactic environments using a semianalytic galaxy formation model and apply our model to a volume-limited low-redshift ($0.03\leqslant z\leqslant 0.1$) sample of observed AGNs to determine the distribution of jet powers and active lifetimes at the present epoch. Radio sources in massive galaxies are found to remain active for longer, spend less time in the quiescent phase, and inject more energy into their hosts than their less massive counterparts. The jet power is independent of the host stellar mass within uncertainties, consistent with maintenance-mode AGN feedback paradigm. The environments of these AGNs are in or close to long-term heating–cooling balance. We also examine the properties of high- and low-excitation radio galactic subpopulations. The HERGs are younger than LERGs by an order of magnitude, whereas their jet powers are greater by a factor of four. The Eddington-scaled accretion rates and jet production efficiencies of these populations are consistent with LERGs being powered by radiatively inefficient advection-dominated accretion flows, whereas HERGs are fed by a radiatively efficient accretion mechanism.

An on-going effort in the characterization of exoplanetary systems is the accurate determination of host star properties. This effort extends to the relatively bright host stars of planets discovered with the radial velocity method. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is aiding in these efforts as part of its observational campaign for exoplanet host stars. One of the first known systems is that of 70 Virginis, which harbors a jovian planet in an eccentric orbit. Here we present a complete characterization of this system with a compilation of TERMS photometry, spectroscopy, and interferometry. We provide fundamental properties of the host star through direct interferometric measurements of the radius (1.5% uncertainty) and through spectroscopic analysis. We combined 59 new Keck HIRES radial velocity measurements with the 169 previously published from the ELODIE, Hamilton, and HIRES spectrographs, to calculate a refined orbital solution and construct a transit ephemeris for the planet. These newly determined system characteristics are used to describe the Habitable Zone of the system with a discussion of possible additional planets and related stability simulations. Finally, we present 19 years of precision robotic photometry that constrain stellar activity and rule out central planetary transits for a Jupiter-radius planet at the 5σ level, with reduced significance down to an impact parameter of b = 0.95.

We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index n ∼ 2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains (SGs) and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variations and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant performance gains over previous systems, achieving SGs in excess of 10,000 with a throughput of ∼87% using uncoated Polymicro octagonal fibers. Adding a circular fiber to the fiber train further increases the SG to >20,000, limited by laboratory measurement error. While this fiber system is designed for the Habitable-zone Planet Finder spectrograph, it is more generally applicable to other instruments in the visible and near-infrared. Given the simplicity and low cost, this fiber scrambler could also easily be multiplexed for large multi-object instruments.

We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7–M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8–120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (∼10–100 M_Jup) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each system to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892–0929121 C (40–60 M_Jup) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the ∼40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young low-mass quadruple system in a compact (≲100 AU) configuration. In addition, Li iλ6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (≲200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1'') companions (2MASS J06475229–2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (≳1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the dustiest-known member of the Pleiades.

The interpretation of gravitational microlensing events caused by planetary systems or multiple stars is based on the n-point-mass lens model. The first planets detected by microlensing were well described by the two-point-mass model of a star with one planet. By the end of 2014, four events involving three-point-mass lenses had been announced. Two of the lenses were stars with two planetary companions each; two were binary stars with a planet orbiting one component. While the two-point-mass model is well understood, the same cannot be said for lenses with three or more components. Even the range of possible critical-curve topologies and caustic geometries of the three-point-mass lens remains unknown. In this paper we provide new tools for mapping the critical-curve topology and caustic cusp number in the parameter space of n-point-mass lenses. We perform our analysis in the image plane of the lens. We show that all contours of the Jacobian are critical curves of re-scaled versions of the lens configuration. Utilizing this property further, we introduce the cusp curve to identify cusp-image positions on all contours simultaneously. In order to track cusp-number changes in caustic metamorphoses, we define the morph curve, which pinpoints the positions of metamorphosis-point images along the cusp curve. We demonstrate the usage of both curves on simple two- and three-point-mass lens examples. For the three simplest caustic metamorphoses we illustrate the local structure of the image and source planes.

We develop a numerical formalism for calculating the distribution with energy of the (internal) pairs formed in a relativistic source from unscattered MeV–TeV photons. For gamma-ray burst (GRB) afterglows, this formalism is more suitable if the relativistic reverse shock that energizes the ejecta is the source of the GeV photons. The number of pairs formed is set by the source GeV output (calculated from the Fermi-LAT fluence), the unknown source Lorentz factor, and the unmeasured peak energy of the LAT spectral component. We show synchrotron and inverse-Compton light curves expected from pairs formed in the shocked medium and identify some criteria for testing a pair origin of GRB optical counterparts. Pairs formed in bright LAT afterglows with a Lorentz factor in the few hundreds may produce bright optical counterparts ($R\lt 10$) lasting for up to one hundred seconds. The number of internal pairs formed from unscattered seed photons decreases very strongly with the source Lorentz factor, thus bright GRB optical counterparts cannot arise from internal pairs if the afterglow Lorentz factor is above several hundreds.

We present the first broadband 0.3–25.0 keV X-ray observations of the bright ultraluminous X-ray source (ULX) Holmberg II X-1, performed by NuSTAR, XMM-Newton, and Suzaku in 2013 September. The NuSTAR data provide the first observations of Holmberg II X-1 above 10 keV and reveal a very steep high-energy spectrum, similar to other ULXs observed by NuSTAR to date. These observations further demonstrate that ULXs exhibit spectral states that are not typically seen in Galactic black hole binaries. Comparison with other sources implies that Holmberg II X-1 accretes at a high fraction of its Eddington accretion rate and possibly exceeds it. The soft X-ray spectrum ($E\lt 10$ keV) appears to be dominated by two blackbody-like emission components, the hotter of which may be associated with an accretion disk. However, all simple disk models under-predict the NuSTAR data above ∼10 keV and require an additional emission component at the highest energies probed, implying the NuSTAR data does not fall away with a Wien spectrum. We investigate physical origins for such an additional high-energy emission component and favor a scenario in which the excess arises from Compton scattering in a hot corona of electrons with some properties similar to the very high state seen in Galactic binaries. The observed broadband 0.3–25.0 keV luminosity inferred from these epochs is ${{L}_{X}}=(8.1\pm 0.1)\times {{10}^{39}}$ erg s⁻¹, typical for Holmberg II X-1, with the majority of this flux (∼90%) emitted below 10 keV.

Cosmological applications of the "redshift—angular size" test require knowledge of the linear size of the "standard rod" used. In this paper, we study the properties of a large sample of 140 mas compact radio sources with flux densities measured at 6 and 20 cm, compiled by Gurvits et al. Using the best-fitted cosmological parameters given by Planck/WMAP9 observations, we investigate the characteristic length l_m, as well as its dependence on the source luminosity L and redshift l_m = lL^β (1 + z)ⁿ. For the full sample, measurements of the angular size θ provide a tight constraint on the linear size parameters. We find that cosmological evolution of the linear size is small $(|n|\simeq {{10}^{-2}})$and consistent with previous analysis. However, a substantial evolution of linear sizes with luminosity is still required (β ≃ 0.17). Furthermore, similar analysis done on sub-samples defined by different source optical counterparts and different redshift ranges seems to support the scheme of treating radio galaxies and quasars with distinct strategies. Finally, a cosmological-model-independent method is discussed to probe the properties of the angular size of milliarcsecond radio quasars. Using the corrected redshift—angular size relation for the quasar sample, we obtained a value of the matter density parameter, ${{{\Omega }}_{m}}=0.292_{-0.090}^{+0.065}$, in the spatially flat ΛCDM cosmology.

We present a framework for high-redshift ($z\gtrsim 7$) galaxy formation that traces their dark matter (DM) and baryonic assembly in four cosmologies: cold dark matter (CDM) and warm dark matter (WDM) with particle masses of $\;{{m}_{x}}$ = 1.5, 3, and 5 $\;{\rm keV}$. We use the same astrophysical parameters regulating star formation and feedback, chosen to match current observations of the evolving ultraviolet luminosity function (UV LF). We find that the assembly of observable (with current and upcoming instruments) galaxies in CDM and $\;{{m}_{x}}\geqslant 3\;\;{\rm keV}$ WDM results in similar halo mass-to-light ratios (M/L), stellar mass densities (SMDs), and UV LFs. However, the suppression of small-scale structure leads to a notably delayed and subsequently more rapid stellar assembly in the $1.5\;\;{\rm keV}$ WDM model. Thus, galaxy assembly in $\;{{m}_{x}}\lesssim 2\;{\rm keV}$ WDM cosmologies is characterized by (1) a dearth of small-mass halos hosting faint galaxies and (2) a younger, more UV-bright stellar population, for a given stellar mass. The higher M/L (effect 2) partially compensates for the dearth of small-mass halos (effect 1), making the resulting UV LFs closer to CDM than expected from simple estimates of halo abundances. We find that the redshift evolution of the SMD is a powerful probe of the nature of DM. Integrating down to a limit of ${{M}_{{\rm UV}}}=-16.5$ for the James Webb Space Telescope (JWST), the SMD evolves as ${\rm log}$(SMD) $\propto -0.63(1+z)$ in $\;{{m}_{x}}=1.5\;{\rm keV}$ WDM, as compared to ${\rm log}$(SMD) $\propto -0.44(1+z)$ in CDM. Thus, high-redshift stellar assembly provides a powerful test bed for WDM models, accessible with the upcoming JWST.

Galaxy clusters exhibit remarkable self-similar behavior which allows us to establish simple scaling relationships between observable quantities and cluster masses, making galaxy clusters useful cosmological probes. Recent X-ray observations suggested that self-similarity may be broken in the outskirts of galaxy clusters. In this work, we analyze a mass-limited sample of massive galaxy clusters from the Omega500 cosmological hydrodynamic simulation to investigate the self-similarity of the diffuse X-ray emitting intracluster medium (ICM) in the outskirts of galaxy clusters. We find that the self-similarity of the outer ICM profiles is better preserved if they are normalized with respect to the mean density of the universe, while the inner profiles are more self-similar when normalized using the critical density. However, the outer ICM profiles as well as the location of accretion shock around clusters are sensitive to their mass accretion rate, which causes the apparent breaking of self-similarity in cluster outskirts. We also find that the collisional gas does not follow the distribution of collisionless dark matter (DM) perfectly in the infall regions of galaxy clusters, leading to 10% departures in the gas-to-DM density ratio from the cosmic mean value. Our results have a number implications for interpreting observations of galaxy clusters in X-ray and through the Sunyaev–Zel'dovich effect, and their applications to cosmology.

We report measurements of the diffuse galactic light (DGL) spectrum in the near-infrared, spanning the wavelength range 0.95–1.65 μm by the Cosmic Infrared Background ExpeRiment. Using the low-resolution spectrometer calibrated for absolute spectro-photometry, we acquired long-slit spectral images of the total diffuse sky brightness toward six high-latitude fields spread over four sounding rocket flights. To separate the DGL spectrum from the total sky brightness, we correlated the spectral images with a 100 μm intensity map, which traces the dust column density in optically thin regions. The measured DGL spectrum shows no resolved features and is consistent with other DGL measurements in the optical and at near-infrared wavelengths longer than 1.8 μm. Our result implies that the continuum is consistently reproduced by models of scattered starlight in the Rayleigh scattering regime with a few large grains.

We utilize observations of sub-millimeter rotational transitions of CO from a Herschel Cycle 2 open time program ("COPS", PI: J. Green) to identify previously predicted turbulent dissipation by magnetohydrodynamic (MHD) shocks in molecular clouds. We find evidence of the shocks expected for dissipation of MHD turbulence in material not associated with any protostar. Two models fit about equally well: model 1 has a density of 10³ cm⁻³, a shock velocity of 3 km s⁻¹, and a magnetic field strength of 4 μG; model 2 has a density of 10^3.5 cm⁻³, a shock velocity of 2 km s⁻¹, and a magnetic field strength of 8 μG. Timescales for decay of turbulence in this region are comparable to crossing times. Transitions of CO up to J of 8, observed close to active sites of star formation, but not within outflows, can trace turbulent dissipation of shocks stirred by formation processes. Although the transitions are difficult to detect at individual positions, our Herschel-SPIRE survey of protostars provides a grid of spatially distributed spectra within molecular clouds. We averaged all spatial positions away from known outflows near seven protostars. We find significant agreement with predictions of models of turbulent dissipation in slightly denser (10^3.5 cm⁻³) material with a stronger magnetic field (24 μG) than in the general molecular cloud.

Recent observations by the Large Area Telescope on board the Fermi satellite have revealed bright γ-ray emission from middle-aged supernova remnants (SNRs) inside our Galaxy. These remnants, which also possess bright non-thermal radio shells, are often found to be interacting directly with surrounding gas clouds. We explore the non-thermal emission mechanism at these dynamically evolved SNRs by constructing a hydrodynamical model. Two scenarios of particle acceleration, either a re-acceleration of Galactic cosmic rays or an efficient nonlinear diffusive shock acceleration (NLDSA) of particles injected from downstream, are considered. Using parameters inferred from observations, our models are contrasted with the observed spectra of SNR W44. For the re-acceleration case, we predict a significant enhancement of radio and GeV emission as the SNR undergoes a transition into the radiative phase. If sufficiently strong magnetic turbulence is present in the molecular cloud, the re-acceleration scenario can explain the observed broadband spectral properties. The NLDSA scenario also succeeds in explaining the γ-ray spectrum but fails to reproduce the radio spectral index. Efficient NLDSA also results in a significant post-shock non-thermal pressure that limits the compression during cooling and prevents the formation of a prominent dense shell. Some other interesting differences between the two models in hydrodynamical behavior and resulting spectral features are illustrated.

We describe and execute a novel approach to observationally estimate the lifetimes of giant molecular clouds (GMCs). We focus on the cloud population between the two main spiral arms in M51 (the inter-arm region) where cloud destruction via shear and star formation feedback dominates over formation processes. By monitoring the change in GMC number densities and properties across the inter-arm, we estimate the lifetime as a fraction of the inter-arm travel time. We find that GMC lifetimes in M51's inter-arm are finite and short, 20–30 Myr. Over most of the region under investigation shear appears to regulate the lifetime. As the shear timescale increases with galactocentric radius, we expect cloud destruction to switch primarily to feedback at larger radii. We identify a transition from shear- to feedback-dominated disruption, finding that shear is more efficient at dispersing clouds, whereas feedback transforms the population, e.g., by fragmenting high-mass clouds into lower mass pieces. Compared to the characteristic timescale for molecular hydrogen in M51, our short lifetimes suggest that gas can remain molecular while clouds disperse and reassemble. We propose that galaxy dynamics regulates the cycling of molecular material from diffuse to bound (and ultimately star-forming) objects, contributing to long observed molecular depletion times in normal disk galaxies. We also speculate that, in extreme environments like elliptical galaxies and concentrated galaxy centers, star formation can be suppressed when the shear timescale is short enough that some clouds will not survive to form stars.

We examine binary systems where when the more massive star, the primary, explodes as a core-collapse supernova (SN), the secondary star is already a giant that intercepts a large fraction of the ejecta. The ejecta might pollute the secondary star with newly synthesized elements such as calcium. We use Modules for Experiments in Stellar Astrophysics to calculate the evolution of such SN-polluted giant (SNPG) binaries. We estimate that on average at any given time tens of SNPGs are present in the Galaxy, and $\approx 10$ SNPG objects are present in the Magellanic Clouds. We speculate that the high calcium abundance of the recently discovered evolved star HV 2112 in the Small Magellanic Cloud might be the result of an SNPG with a super-AGB stellar secondary of mass $\approx 9\;{{M}_{\odot }}$. This rare SNPG scenario is an alternative explanation to HV 2112 being a Thorne–Żytkow object.

Anomalous ammonia (NH₃) spectra, exhibiting asymmetric hyperfine satellite intensity profiles in the ($J,K$) = (1, 1) inversion transition, have been observed in star-forming regions for over 35 years. We present a systematic study of this "hyperfine intensity anomaly" (HIA) toward a sample of 334 high-mass star forming regions: 310 high-mass (≳100 ${{M}_{\odot }}$) clumps and 24 infrared dark clouds. The HIA is ubiquitous in high-mass star forming regions. Although LTE excitation predicts that the intensity ratios of the outer satellites and inner satellites are exactly unity, for this sample the ensemble average ratios are 0.812 ± 0.004 and 1.125 ± 0.005, respectively. We have quantified the HIA and find no significant relationships between the HIA and temperature, line width, optical depth, and the stage of stellar evolution. The fact that HIAs are common in high-mass star-forming regions suggests that the conditions that lead to HIAs are ubiquitous in these regions. A possible link between HIAs and the predictions of the competitive accretion model of high-mass star formation is suggested; however, the expected trends of HIA strength with clump evolutionary stage, rotational temperature, and line width for evolving cores in competitive accretion models are not found. Thus, the exact gas structures that produce HIAs remain unknown. Turbulent gas structures are a possible explanation, but the details need to be explored.

We have used the Submillimeter Array to image, at ∼15 resolution, C₂H $N=3\to 2$ emission from the circumstellar disk orbiting the nearby (D = 54 pc), ∼8 Myr-old, ∼0.8 ${{M}_{\odot }}$ classical T Tauri star TW Hya. The SMA imaging reveals that the C₂H emission exhibits a ring-like morphology. Based on a model in which the C₂H column density follows a truncated radial power-law distribution, we find that the inner edge of the ring lies at ∼45 AU, and that the ring extends to at least ∼120 AU. Comparison with previous (single-dish) observations of C₂H $N=4\to 3$ emission indicates that the C₂H molecules are subthermally excited and, hence, that the emission arises from the relatively warm ($T\gtrsim 40$ K), tenuous ($n\ll {{10}^{7}}$ cm⁻³) upper atmosphere of the disk. Based on these results and comparisons of the SMA C₂H map with previous submillimeter and scattered-light imaging, we propose that the C₂H emission most likely traces particularly efficient photo-destruction of small grains and/or photodesorption and photodissociation of hydrocarbons derived from grain ice mantles in the surface layers of the outer disk. The presence of a C₂H ring in the TW Hya disk hence likely serves as a marker of dust grain processing and radial and vertical grain size segregation within the disk.

We calculate the long-term evolution of angular momentum in double white dwarf binaries undergoing direct impact accretion over a broad range of parameter space. We allow the rotation rate of both components to vary and account for the exchange of angular momentum between the spins of the white dwarfs and the orbit, while conserving the total angular momentum. We include gravitational, tidal, and mass transfer effects in the orbital evolution, and allow the Roche radius of the donor star to vary with both the stellar mass and the rotation rate. We examine the long-term stability of these systems, focusing in particular on those systems that may be progenitors of AM CVn or SNe Ia. We find that our analysis yields an increase in the predicted number of stable systems compared to that in previous studies. Additionally, we find that by properly accounting for the effects of asynchronism between the donor and the orbit on the Roche-lobe size, we eliminate oscillations in the orbital parameters, which were found in previous studies. Removing these oscillations can reduce the peak mass transfer rate in some systems, keeping them from entering an unstable mass transfer phase.

The solar system contains solids of all sizes, ranging from kilometer-sized bodies to nano-sized particles. Nanograins have been detected in situ in the Earth's atmosphere, near cometary and giant planet environments, and more recently in the solar wind at 1 AU. The latter nanograins are thought to be formed in the inner solar system dust cloud, mainly through the collisional break-up of larger grains, and are then picked up and accelerated by the magnetized solar wind because of their large charge-to-mass ratio. In the present paper, we analyze the low frequency bursty noise identified in the Cassini radio and plasma wave data during the spacecraft cruise phase inside Jupiter's orbit. The magnitude, spectral shape, and waveform of this broadband noise are consistent with the signatures of the nano particles that traveled at solar wind speed and impinged on the spacecraft surface. Nanoparticles were observed whenever the radio instrument was turned on and able to detect them at different heliocentric distances between Earth and Jupiter, suggesting their ubiquitous presence in the heliosphere. We analyzed the radial dependence of the nanodust flux with heliospheric distance and found that it is consistent with the dynamics of nanodust originating from the inner heliosphere and picked up by the solar wind. The contribution of the nanodust produced in the asteroid belt appears to be negligible compared to the trapping region in the inner heliosphere. In contrast, further out, nanodust is mainly produced by the volcanism of active moons such as Io and Enceladus.

The absolute value of the magnetic helicity spectrum of the solar wind turbulence often has a peak at kinetic scales. This helicity signature is important for understanding the mechanism of the turbulent cascade. In this paper, a statistical analysis of the magnetic helicity is performed. For this purpose, a database of the solar wind intervals with the helicity signature was assembled using Wind spacecraft magnetic and plasma data. New statistically significant correlations between the magnetic helicity and the properties of the background plasma are found. The position of the signature within the spectrum depends on the proton gyroscale and the proton inertial scale. Possible mechanisms responsible for the observed trends are discussed. The helicity peak is interpreted as a result of two competing processes, one of which generates the helicity and the other one eliminates it.

δ-sunspots, with highly complex magnetic structures, are very productive in energetic eruptive events, such as X-class flares and homologous eruptions. We here study the formation of such complex magnetic structures by numerical simulations of magnetic flux emergence from the convection zone into the corona in an active-region-scale domain. In our simulation, two pairs of bipolar sunspots form on the surface, originating from two buoyant segments of a single subsurface twisted flux rope, following the approach of Toriumi et al. Expansion and rotation of the emerging fields in the two bipoles drive the two opposite polarities into each other with apparent rotating motion, producing a compact δ-sunspot with a sharp polarity inversion line. The formation of the δ-sunspot in such a realistic-scale domain produces emerging patterns similar to those formed in observations, e.g., the inverted polarity against Hale's law, the curvilinear motion of the spot, and strong transverse field with highly sheared magnetic and velocity fields at the polarity inversion line (PIL). Strong current builds up at the PIL, giving rise to reconnection, which produces a complex coronal magnetic connectivity with non-potential fields in the δ-spot overlaid by more relaxed fields connecting the two polarities at the two ends.

With the first observations of solar γ-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the γ-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported back to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the γ-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space.

We analyze coordinated observations of coronal rain in loops, spanning chromospheric, transition region (TR), and coronal temperatures with sub-arcsecond spatial resolution. Coronal rain is found to be a highly multithermal phenomenon with a high degree of co-spatiality in the multi-wavelength emission. EUV darkening and quasi-periodic intensity variations are found to be strongly correlated with coronal rain showers. Progressive cooling of coronal rain is observed, leading to a height dependence of the emission. A fast-slow two-step catastrophic cooling progression is found, which may reflect the transition to optically thick plasma states. The intermittent and clumpy appearance of coronal rain at coronal heights becomes more continuous and persistent at chromospheric heights just before impact, mainly due to a funnel effect from the observed expansion of the magnetic field. Strong density inhomogeneities of $0\buildrel{\prime\prime}\over{.} 2-0\buildrel{\prime\prime}\over{.} 5$ are found, in which a transition from temperatures of 10⁵ to 10⁴ K occurs. The $0\buildrel{\prime\prime}\over{.} 2$–$0\buildrel{\prime\prime}\over{.} 8$ width of the distribution of coronal rain is found to be independent of temperature. The sharp increase in the number of clumps at the coolest temperatures, especially at higher resolution, suggests that the bulk distribution of the rain remains undetected. Rain clumps appear organized in strands in both chromospheric and TR temperatures. We further find structure reminiscent of the magnetohydrodynamic (MHD) thermal mode (also known as entropy mode), thereby suggesting an important role of thermal instability in shaping the basic loop substructure. Rain core densities are estimated to vary between 2 × 10¹⁰ and $2.5\times {{10}^{11}}$ cm⁻³, leading to significant downward mass fluxes per loop of 1–5 × 10⁹ g s⁻¹, thus suggesting a major role in the chromosphere-corona mass cycle.

Stellar population synthesis (SPS) models are used to infer many galactic properties including star formation histories, metallicities, and stellar and dust masses. However, most SPS models neglect the effect of circumstellar dust shells around evolved stars and it is unclear to what extent they impact the analysis of spectral energy distributions (SEDs). To overcome this shortcoming we have created a new set of circumstellar dust models, using the radiative transfer code DUSTY, for asymptotic giant branch (AGB) stars and incorporated them into the Flexible Stellar Population Synthesis code. The circumstellar dust models provide a good fit to individual AGB stars as well as the IR color–magnitude diagrams of the Large and Small Magellanic Clouds. IR luminosity functions from the Large and Small Magellanic Clouds are not well-fit by the 2008 Padova isochrones when coupled to our circumstellar dust models and so we adjusted the lifetimes of AGB stars in the models to provide a match to the data. We show, in agreement with previous work, that circumstellar dust from AGB stars can make a significant contribution to the IR ($\gtrsim 4\;\mu {\rm m}$) emission from galaxies that contain relatively little diffuse dust, including low-metallicity and/or non-star-forming galaxies. Our models provide a good fit to the mid-IR spectra of early-type galaxies. Circumstellar dust around AGB stars appears to have a small effect on the IR SEDs of metal-rich star-forming galaxies (i.e., when A_V ≳ 0.1). Stellar population models that include circumstellar dust will be needed to accurately interpret data from the James Webb Space Telescope and other IR facilities.

We use the integrated polarized radio emission at 1.4 GHz (${{{\Pi }}_{1.4\,{\rm GHz}}}$) from a large sample of active galactic nuclei (AGN; 796 sources at redshifts $z\lt 0.7$) to study the large-scale magnetic field properties of radio galaxies in relation to the host galaxy accretion state. We find a fundamental difference in ${{{\Pi }}_{1.4\,{\rm GHz}}}$ between radiative-mode AGN (i.e., high-excitation radio galaxies (HERGs) and radio-loud QSOs) and jet-mode AGN (i.e., low-excitation radio galaxies (LERGs)). While LERGs can achieve a wide range of ${{{\Pi }}_{1.4\,{\rm GHz}}}$ (up to ∼30%), the HERGs and radio-loud QSOs are limited to ${{{\Pi }}_{1.4\,{\rm GHz}}}\lesssim 15\%$. A difference in ${{{\Pi }}_{1.4\,{\rm GHz}}}$ is also seen when the sample is divided at 0.5% of the total Eddington-scaled accretion rate, where the weakly accreting sources can attain higher values of ${{{\Pi }}_{1.4\,{\rm GHz}}}$. We do not find any clear evidence that this is driven by intrinsic magnetic field differences of the different radio morphological classes. Instead, we attribute the differences in ${{{\Pi }}_{1.4\,{\rm GHz}}}$ to the local environments of the radio sources, in terms of both the ambient gas density and the magnetoionic properties of this gas. Thus, not only are different large-scale gaseous environments potentially responsible for the different accretion states of HERGs and LERGs, we argue that the large-scale magnetized environments may also be important for the formation of powerful AGN jets. Upcoming high angular resolution and broadband radio polarization surveys will provide the high-precision Faraday rotation measure and depolarization data required to robustly test this claim.

We present optical integral field spectroscopy of the circum-nuclear gas of the Seyfert 2 galaxy NGC 1386. The data cover the central 7'' × 9'' (530 × 680 pc) at a spatial resolution of 0 9 (68 pc), and the spectral range 5700–7000 Å at a resolution of 66 km s⁻¹. The line emission is dominated by a bright central component, with two lobes extending ≈3'' north and south of the nucleus. We identify three main kinematic components. The first has low velocity dispersion ($\bar{\sigma }\;\approx$ 90 km s⁻¹), extends over the whole field of view, and has a velocity field consistent with gas rotating in the galaxy disk. We interpret the lobes as resulting from photoionization of disk gas in regions where the active galactic nucleus radiation cones intercept the disk. The second has higher velocity dispersion ($\bar{\sigma }\;\approx$ 200 km s⁻¹) and is observed in the inner 150 pc around the continuum peak. This component is double peaked, with redshifted and blueshifted components separated by ≈500 km s⁻¹. Together with previous Hubble Space Telescope imaging, these features suggest the presence of a bipolar outflow for which we estimate a mass outflow rate of $\dot{M}\;\gtrsim$ 0.1 ${{M}_{\odot }}$ yr⁻¹. The third component is revealed by velocity residuals associated with enhanced velocity dispersion and suggests that outflow and/or rotation is occurring approximately in the equatorial plane of the torus. A second system of velocity residuals may indicate the presence of streaming motions along dusty spirals in the disk.

We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes M_r < −19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 ± 0.003) is higher than that in all relaxed clusters (0.097 ± 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters.

Hydrocarbon organic material, as found in the interstellar medium, exists in complex mixtures of aromatic and aliphatic forms. It is considered to originate from carbon-enriched giant stars during their final stages of evolution, when very strong mass loss occurs in a few thousand years on their way to becoming planetary nebulae. We show here that the same organic compounds appear to be formed in previous stages of the evolution of giant stars, more specifically, during the first-ascending giant branch K-type stars. According to our model, this happens only when these stars are being abruptly enriched with lithium, together with the formation of a circumstellar shell with a strong mass loss during just a few thousand years. This sudden mass loss is, on average, a thousand times larger than that of normal Li-poor K giant stars. This shell would later be detached, especially when the star stops its Li enrichment and a rapid photospheric Li depletion occurs. In order to gain extra carbon-based material to form the organic hydrocarbons, as well as to explain the presence of complex inorganic compounds in these stars, we propose an interaction of these strong winds with the remaining asteroidal/cometary disks that already existed around these stars since they were dwarf A-type stars. The mechanism of interaction presented here is successful in explaining the presence of inorganic compounds; however, it is unable to produce new carbon-free atoms to form the organic hydrocarbon compounds. Finally, we discuss some suggestions and speculations that can eventually help solve the long-standing puzzle of Li-rich giants.

We search for electron anti-neutrinos (${{\bar{\nu }}_{e}}$) from long- and short-duration gamma-ray bursts (GRBs) using data taken by the Kamioka Liquid Scintillator Anti-Neutrino Detector (KamLAND) from 2002 August to 2013 June. No statistically significant excess over the background level is found. We place the tightest upper limits on ${{\bar{\nu }}_{e}}$ fluence from GRBs below 7 MeV and place first constraints on the relation between ${{\bar{\nu }}_{e}}$ luminosity and effective temperature.

We consider the evolution of a supermassive black hole binary (SMBHB) surrounded by a retrograde accretion disk. Assuming the disk is exactly in the binary plane and transfers energy and angular momentum to the binary via direct gas accretion, we calculate the time evolution of the binaryʼs semimajor axis a and eccentricity e. Because the gas is predominantly transferred when the binary is at apocenter, we find the eccentricity grows rapidly while maintaining constant $a(1+e)$. After accreting only a fraction of the secondaryʼs mass, the eccentricity grows to nearly unity; from then on, gravitational wave (GW) emission dominates the evolution, preserving constant $a(1-e)$. The high-eccentricity waveforms redistribute the peak GW power from the nHz to μHz bands, substantially affecting the signal that might be detected with pulsar timing arrays. We also estimate the torque coupling binaries of arbitrary eccentricity with obliquely aligned circumbinary disks. If the outer edge of the disk is not an extremely large multiple of the binary separation, retrograde accretion can drive the binary into the GW-dominated state before these torques align the binary with the angular momentum of the mass supply.

Type I X-ray bursts on the surface of a neutron star are a unique probe into accretion in X-ray binary systems. However, we know little about the feedback of the burst emission on accretion. Hard X-ray shortages and enhancements of the persistent emission at soft X-rays have been observed. To put these findings in context with the aim of understanding the possible mechanism underneath, we investigated 68 bursts seen by the Rossi X-ray Timing Explorer from the clocked burster GS 1826-238. We diagnosed jointly the burst influence of both soft and hard X-rays, and we found that the observations can be described by the CompTT model with variable normalization, electron temperature, and optical depth. Putting these results in a scenario of coronal Compton cooling via the burst emission would lead to a shortage of cooling power, which may suggest that additional considerations, like the influence of the burst on corona formation, should be accounted for as well.

We have studied the aperiodic variability of the 401 Hz accreting millisecond X-ray pulsar SAX J1808.4−3658 using the complete data set collected with the Rossi X-ray Timing Explorer over 14 years of observation. The source shows a number of exceptional aperiodic timing phenomena that are observed against a backdrop of timing properties that show consistent trends in all five observed outbursts and closely resemble those of other atoll sources. We performed a detailed study of the enigmatic ∼410 Hz quasi-periodic oscillation (QPO), which has only been observed in SAX J1808.4−3658. We find that it appears only when the upper kHz QPO frequency is less than the 401 Hz spin frequency. The difference between the ∼410 Hz QPO frequency and the spin frequency follows a similar frequency correlation as the low frequency power spectral components, suggesting that the ∼410 Hz QPO is a retrograde beat against the spin frequency of a rotational phenomenon in the 9 Hz range. Comparing this 9 Hz beat feature with the low-frequency QPO in SAX J1808.4−3658 and other neutron star sources, we conclude that these two might be part of the same basic phenomenon. We suggest that they might be caused by retrograde precession due to a combination of relativistic, classical and magnetic torques. Additionally we present two new measurements of the lower kHz QPO, allowing us, for the first time, to measure the frequency evolution of the twin kHz QPOs in this source. The twin kHz QPOs are seen to move together over 150 Hz, maintaining a centroid frequency separation of $(0.446\pm 0.009){\nu }_{\mathrm{spin}}$.

The 1.69 ms spin period of PSR J1227−4853 was recently discovered in radio observations of the low-mass X-ray binary XSS J12270−4859 following the announcement of a possible transition to a rotation-powered millisecond pulsar state, inferred from decreases in optical, X-ray, and gamma-ray flux from the source. We report the detection of significant (5σ) gamma-ray pulsations after the transition, at the known spin period, using ∼1 year of data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray light curve of PSR J1227−4853 can be fit by one broad peak, which occurs at nearly the same phase as the main peak in the 1.4 GHz radio profile. The partial alignment of light-curve peaks in different wavebands suggests that at least some of the radio emission may originate at high altitude in the pulsar magnetosphere, in extended regions co-located with the gamma-ray emission site. We folded the LAT data at the orbital period, both pre- and post-transition, but find no evidence for significant modulation of the gamma-ray flux. Analysis of the gamma-ray flux over the mission suggests an approximate transition time of 2012 November 30. Continued study of the pulsed emission and monitoring of PSR J1227−4853, and other known redback systems, for subsequent flux changes will increase our knowledge of the pulsar emission mechanism and transitioning systems.

We present a dynamical study of the Galactic black hole binary system Nova Muscae 1991 (GS/GRS 1124–683). We utilize 72 high-resolution Magellan Echellette spectra and 72 strictly simultaneous V-band photometric observations; the simultaneity is a unique and crucial feature of this dynamical study. The data were taken on two consecutive nights and cover the full 10.4 hr orbital cycle. The radial velocities of the secondary star are determined by cross-correlating the object spectra with the best-match template spectrum obtained using the same instrument configuration. Based on our independent analysis of five orders of the echellette spectrum, the semi-amplitude of the radial velocity of the secondary is measured to be ${{K}_{2}}=406.8\pm 2.7$ km s⁻¹, which is consistent with previous work, while the uncertainty is reduced by a factor of 3. The corresponding mass function is $f(M)=3.02\pm 0.06\ {{M}_{\odot }}$. We have also obtained an accurate measurement of the rotational broadening of the stellar absorption lines ($v{\rm sin} i=85.0\pm 2.6$ km s⁻¹), and hence the mass ratio of the system $q=0.079\pm 0.007$. Finally, we have measured the spectrum of the non-stellar component of emission that veils the spectrum of the secondary. In a future paper, we will use our veiling-corrected spectrum of the secondary and accurate values of K₂ and q to model multi-color light curves and determine the systemic inclination and the mass of the black hole.

We apply our two-dimensional (2D), radially self-similar steady-state accretion flow model to the analysis of hydrodynamic simulation results of supercritical accretion flows. Self-similarity is checked and the input parameters for the model calculation, such as advective factor and heat capacity ratio, are obtained from time-averaged simulation data. Solutions of the model are then calculated and compared with the simulation results. We find that in the converged region of the simulation, excluding the part too close to the black hole, the radial distributions of azimuthal velocity ${{v}_{\phi }}$, density ρ and pressure p basically follow the self-similar assumptions, i.e., they are roughly proportional to ${{r}^{-0.5}}$, ${{r}^{-n}}$, and ${{r}^{-(n+1)}}$, respectively, where $n\sim 0.85$ for the mass injection rate of $1000{{L}_{{\rm E}}}/{{c}^{2}}$, and $n\sim 0.74$ for $3000{{L}_{{\rm E}}}/{{c}^{2}}$. The distribution of v_r and ${{v}_{\theta }}$ agrees less with self-similarity, possibly due to convective motions in the $r\theta$ plane. The distribution of velocity, density, and pressure in the θ direction obtained by the steady model agrees well with the simulation results within the calculation boundary of the steady model. Outward mass flux in the simulations is overall directed toward a polar angle of 0.8382 rad ($\sim 48\buildrel{\circ}\over{.} 0$) for $1000{{L}_{{\rm E}}}/{{c}^{2}}$ and 0.7852 rad ($\sim 43\buildrel{\circ}\over{.} 4$) for $3000{{L}_{{\rm E}}}/{{c}^{2}}$, and ∼94% of the mass inflow is driven away as outflow, while outward momentum and energy fluxes are focused around the polar axis. Parts of these fluxes lie in the region that is not calculated by the steady model, and special attention should be paid when the model is applied.

We present a new optical polarimetric catalog for the Small Magellanic Cloud (SMC). It contains a total of 7207 stars, located in the northeast (NE) and Wing sections of the SMC and part of the Magellanic Bridge. This new catalog is a significant improvement compared to previous polarimetric catalogs for the SMC. We used it to study the sky-projected interstellar magnetic field structure of the SMC. Three trends were observed for the ordered magnetic field direction at position angles (PAs) of (65° ± 10°), (115° ± 10°), and (150° ± 10°). Our results suggest the existence of an ordered magnetic field aligned with the Magellanic Bridge direction and SMC's Bar in the NE region, which have PAs roughly at 1154 and 45°, respectively. However, the overall magnetic field structure is fairly complex. The trends at 115° and 150° may be correlated with the SMC's bimodal structure, observed in Cepheids' distances and HI velocities. We derived a value of ${{B}_{{\rm sky}}}=(0.947\pm 0.079)$μG for the ordered sky-projected magnetic field, and $\delta B=(1.465\pm 0.069)$μG for the turbulent magnetic field. This estimate of ${{B}_{{\rm sky}}}$ is significantly larger (by a factor of ∼10) than the line of sight field derived from Faraday rotation observations, suggesting that most of the ordered field component is on the plane of the sky. A turbulent magnetic field stronger than the ordered field agrees with observed estimates for other irregular and spiral galaxies. For the SMC the ${{B}_{{\rm sky}}}/\delta B$ ratio is closer to what is observed for our Galaxy than other irregular dwarf galaxies.

We report five Local Volume dwarf galaxies (two of which are presented here for the first time) uncovered during a comprehensive archival search for optical counterparts to ultra-compact high-velocity clouds (UCHVCs). The UCHVC population of HI clouds are thought to be candidate gas-rich, low-mass halos at the edge of the Local Group and beyond, but no comprehensive search for stellar counterparts to these systems has been presented. Careful visual inspection of all publicly available optical and ultraviolet imaging at the position of the UCHVCs revealed six blue, diffuse counterparts with a morphology consistent with a faint dwarf galaxy beyond the Local Group. Optical spectroscopy of all six candidate dwarf counterparts show that five have an Hα-derived velocity consistent with the coincident HI cloud, confirming their association; the sixth diffuse counterpart is likely a background object. The size and luminosity of the UCHVC dwarfs is consistent with other known Local Volume dwarf irregular galaxies. The gas fraction (${{M}_{{\rm HI}}}/{{M}_{{\rm star}}}$) of the five dwarfs are generally consistent with that of dwarf irregular galaxies in the Local Volume, although ALFALFA-Dw1 (associated with ALFALFA UCHVC HVC274.68+74.70–123) has a very high ${{M}_{{\rm HI}}}/{{M}_{{\rm star}}}$ ∼ 40. Despite the heterogenous nature of our search, we demonstrate that the current dwarf companions to UCHVCs are at the edge of detectability due to their low surface brightness, and that deeper searches are likely to find more stellar systems. If more sensitive searches do not reveal further stellar counterparts to UCHVCs, then the dearth of such systems around the Local Group may be in conflict with ΛCDM simulations.

We present improved estimates of several global properties of the Milky Way, including its current star formation rate (SFR), the stellar mass contained in its disk and bulge+bar components, as well as its total stellar mass. We do so by combining previous measurements from the literature using a hierarchical Bayesian (HB) statistical method that allows us to account for the possibility that any value may be incorrect or have underestimated errors. We show that this method is robust to a wide variety of assumptions about the nature of problems in individual measurements or error estimates. Ultimately, our analysis yields an SFR for the Galaxy of ${{{\rm \dot{M}}}_{\star }}=1.65\pm 0.19\;{{{\rm M}}_{\odot }}\;{\rm y}{{{\rm r}}^{-1}}$, assuming a Kroupa initial mass function (IMF). By combining HB methods with Monte Carlo simulations that incorporate the latest estimates of the Galactocentric radius of the Sun, R₀, the exponential scale length of the disk, L_d, and the local surface density of stellar mass, ${{{\Sigma}}_{\star }}({{R}_{0}})$, we show that the mass of the Galactic bulge+bar is ${\rm M}_{\star }^{B}=0.91\pm 0.07\times {{10}^{10}}$${{{\rm M}}_{\odot }}$, the disk mass is ${\rm M}_{\star }^{D}=5.17\pm 1.11\times {{10}^{10}}$${{{\rm M}}_{\odot }}$, and their combination yields a total stellar mass of ${{{\rm M}}_{\star }}=6.08\pm 1.14\times {{10}^{10}}$${{{\rm M}}_{\odot }}$ (assuming a Kroupa IMF and an exponential disk profile). This analysis is based upon a new compilation of literature bulge mass estimates, normalized to common assumptions about the stellar IMF and Galactic disk properties, presented herein. We additionally find a bulge-to-total mass ratio for the Milky Way of $B/T=0.150_{-0.019}^{+0.028}$ and a specific SFR of ${{{\rm \dot{M}}}_{\star }}/{{{\rm M}}_{\star }}=2.71\pm 0.59\times {{10}^{-11}}$ yr⁻¹.

We present results of numerical simulations of flux and linear polarization variations in transiting exoplanetary systems, caused by host star disk symmetry breaking. We consider different configurations of planetary transits depending on orbital parameters. The starspot contribution to the polarized signal is also estimated. Applying the method to known systems and simulating observational conditions, a number of targets is selected where transit polarization effects could be detected. We investigate several principal benefits of the transit polarimetry, particularly for determining orbital spatial orientation and distinguishing between grazing and near-grazing planets. Simulations show that polarization parameters are also sensitive to starspots, and they can be used to determine spot positions and sizes.

We examine characteristics of circumbinary orbits in the context of current planet formation scenarios. Analytical perturbation theory predicts the existence of nested circumbinary orbits that are generalizations of circular paths around a single star. These orbits have forced eccentric motion aligned with the binary as well as higher frequency oscillations, yet they do not cross, even in the presence of massive disks and perturbations from large planets. For this reason, dissipative gas and planetesimals can settle onto these "most circular" orbits, facilitating the growth of protoplanets. Outside a region close to the binary where orbits are generally unstable, circumbinary planets form in much the same way as their cousins around a single star. Here, we review the theory and confirm its predictions with a suite of representative simulations. We then consider the circumbinary planets discovered with NASA's Kepler satellite. These Neptune- and Jupiter-size planets, or their planetesimal precursors, may have migrated inward to reach their observed orbits, since their current positions are outside of unstable zones caused by overlapping resonances. In situ formation without migration seems less likely, only because the surface density of the protoplanetary disks must be implausibly high. Otherwise, the circumbinary environment is friendly to planet formation, and we expect that many earth-like "Tatooines" will join the growing census of circumbinary planets.

Among the 25 planetary systems detected up to now by gravitational microlensing, there are two cases of a star with two planets, and two cases of a binary star with a planet. Other, yet undetected types of triple lenses include triple stars or stars with a planet with a moon. The analysis and interpretation of such events is hindered by the lack of understanding of essential characteristics of triple lenses, such as their critical curves and caustics. We present here analytical and numerical methods for mapping the critical-curve topology and caustic cusp number in the parameter space of n-point-mass lenses. We apply the methods to the analysis of four symmetric triple-lens models, and obtain altogether 9 different critical-curve topologies and 32 caustic structures. While these results include various generic types, they represent just a subset of all possible triple-lens critical curves and caustics. Using the analyzed models, we demonstrate interesting features of triple lenses that do not occur in two-point-mass lenses. We show an example of a lens that cannot be described by the Chang–Refsdal model in the wide limit. In the close limit we demonstrate unusual structures of primary and secondary caustic loops, and explain the conditions for their occurrence. In the planetary limit we find that the presence of a planet may lead to a whole sequence of additional caustic metamorphoses. We show that a pair of planets may change the structure of the primary caustic even when placed far from their resonant position at the Einstein radius.

The rotational spectrum of the mono-deuterated isotopologue of water, HD¹⁶O, has been investigated in the millimeter- and submillimeter-wave frequency regions, up to 1.6 THz. The Lamb-dip technique has been exploited to obtain sub-Doppler resolution and to resolve the hyperfine (hf) structure due to the deuterium and hydrogen nuclei, thus enabling the accurate determination of the corresponding hf parameters. Their experimental determination has been supported by high-level quantum-chemical calculations. The Lamb-dip measurements have been supplemented by Doppler-limited measurements (weak high-J and high-frequency transitions) in order to extend the predictive capability of the available spectroscopic constants. The possibility of resolving hf splittings in astronomical spectra has been discussed.

We present a study of the spatial distribution and kinematics of star-forming galaxies in 30 massive clusters at 0.15 < z < 0.30, combining wide-field Spitzer 24 μm and GALEX near-ultraviolet imaging with highly complete spectroscopy of cluster members. The fraction (f_SF) of star-forming cluster galaxies rises steadily with cluster-centric radius, increasing fivefold by 2r₂₀₀, but remains well below field values even at 3r₂₀₀. This suppression of star formation at large radii cannot be reproduced by models in which star formation is quenched in infalling field galaxies only once they pass within r₂₀₀ of the cluster, but is consistent with some of them being first pre-processed within galaxy groups. Despite the increasing f_SF-radius trend, the surface density of star-forming galaxies actually declines steadily with radius, falling ∼15× from the core to 2r₂₀₀. This requires star formation to survive within recently accreted spirals for 2–3 Gyr to build up the apparent over-density of star-forming galaxies within clusters. The velocity dispersion profile of the star-forming galaxy population shows a sharp peak of 1.44 σ_ν at 0.3r₅₀₀, and is 10%–35% higher than that of the inactive cluster members at all cluster-centric radii, while their velocity distribution shows a flat, top-hat profile within r₅₀₀. All of these results are consistent with star-forming cluster galaxies being an infalling population, but one that must also survive ∼0.5–2 Gyr beyond passing within r₂₀₀. By comparing the observed distribution of star-forming galaxies in the stacked caustic diagram with predictions from the Millennium simulation, we obtain a best-fit model in which star formation rates decline exponentially on quenching timescales of 1.73 ± 0.25 Gyr upon accretion into the cluster.

We present observations carried out using the 10.4 m Gran Telescopio Canarias and an interpretative model of the dust environment of activated asteroid 313 P/Gibbs. We discuss three different models relating to different values of the dust parameters, i.e., dust loss rate, maximum and minimum sizes of particles, power index of the size distribution, and emission pattern. The best model corresponds to an isotropic emission of particles which started on August 1. The sizes of grains were in the range of 0.1−2000 μm, with velocities for 100 μm particles between 0.4−1.9 m s⁻¹, with a dust production rate in the range of 0.2−0.8 kg s⁻¹. The dust tails' brightnesses and morphologies are best interpreted in terms of a model of sustained and low dust emission driven by water-ice sublimation, spanning since 2014 August 1, and triggered by a short impulsive event. This event produced an emission of small particles of about 0.1 μm with velocities of ∼4 m s⁻¹. From our model we deduce that the activity of this main-belt comet continued for at least four months since activation.

Elliptical cluster galaxies are progressively stripped of their atmospheres due to their motion through the intracluster medium (ICM). Deep X-ray observations reveal the fine-structure of the galaxy's remnant atmosphere and its gas tail and wake. This fine-structure depends on dynamic conditions (galaxy potential, initial gas contents, orbit through the host cluster), orbital stage (early infall, pre-/post-pericenter passage), and ICM plasma properties (thermal conductivity, viscosity, magnetic field structure). We aim to disentangle dynamic and plasma effects in order to use stripped ellipticals as probes of ICM plasma properties. This first paper of a series investigates the hydrodynamics of progressive gas stripping by means of inviscid hydrodynamical simulations. We distinguish a long-lasting initial relaxation phase and a quasi-steady stripping phase. During quasi-steady stripping, the ICM flow around the remnant atmosphere resembles the flow around solid bodies, including a "deadwater" region in the near wake. Gas is stripped from the remnant atmosphere predominantly at its sides via Kelvin–Helmholtz instabilities. The downstream atmosphere is largely shielded from the ICM wind and thus shaped into a tail. Observationally, both this "remnant tail" and the stripped gas in the wake can appear as a "tail", but only in the wake can galactic gas mix with the ambient ICM. While the qualitative results are generic, the simulations presented here are tailored to the Virgo elliptical galaxy M89 (NGC 4552) for the most direct comparison to observations. Papers II and III of this series describe the effect of viscosity and compare to Chandra and XMM-Newton observations, respectively.

Elliptical galaxies moving through the intracluster medium (ICM) are progressively stripped of their gaseous atmospheres. X-ray observations reveal the structure of galactic tails, wakes, and the interface between the galactic gas and the ICM. This fine-structure depends on dynamic conditions (galaxy potential, initial gas contents, orbit in the host cluster), orbital stage (early infall, pre-/post-pericenter passage), as well as on the still ill-constrained ICM plasma properties (thermal conductivity, viscosity, magnetic field structure). Paper I describes flow patterns and stages of inviscid gas stripping. Here we study the effect of a Spitzer-like temperature dependent viscosity corresponding to Reynolds numbers, Re, of 50–5000 with respect to the ICM flow around the remnant atmosphere. Global flow patterns are independent of viscosity in this Reynolds number range. Viscosity influences two aspects. In inviscid stripping, Kelvin–Helmholtz instabilities (KHIs) at the sides of the remnant atmosphere lead to observable horns or wings. Increasing viscosity suppresses KHIs of increasing length scale and thus observable horns and wings. Furthermore, in inviscid stripping, stripped galactic gas can mix with the ambient ICM in the galaxy's wake. This mixing is suppressed increasingly with increasing viscosity, such that viscously stripped galaxies have long X-ray bright, cool wakes. We provide mock X-ray images for different stripping stages and conditions. While these qualitative results are generic, we tailor our simulations to the Virgo galaxy M89 (NGC 4552), where $\operatorname{Re}\approx 50$ corresponds to a viscosity of 10% of the Spitzer level. Paper III compares new deep Chandra and archival XMM-Newton data to our simulations.

The beginning of photoionization marks the transition between the post-AGB and planetary nebula (PN) phases of stars with masses $\lesssim 8$M$_{\odot }$. This critical phase is difficult to observe, as it lasts only a few decades. The combination of jets and magnetic fields, the key agents of PN shaping, could give rise to synchrotron emission, but this has never been observed before in any PNe, since free–free emission from the ionized gas is expected to dominate its radio spectrum. In this paper we report radio continuum observations taken with the ATCA between 1 and 46 GHz of the young PN IRAS 15103–5754. Our observations in 2010–2011 show non-thermal emission compatible with synchrotron emission from electrons accelerated at a shock with spectral index $\alpha \simeq -0.54$. However, in 2012, the spectral index $\alpha \simeq -0.28$ is no longer compatible with synchrotron emission in these types of processes. Several hypotheses are discussed to explain this change. The more plausible ones are related to the presence of the newly photoionized region in this young PN: either energy loss of electrons due to Coulomb collisions with the plasma, or selective suppression of synchrotron radiation due to the Razin effect. We postulate that the observed flattening of non-thermal radio spectra could be a hallmark identifying the beginning of the PN phase.

We revisit the exquisite archival radio data for the Type Ic supernova SN 1994I and present a revised model for the supernova (SN) radio emission and a pilot study that aims to constrain the rate of C-band radio transients within the face-on host galaxy, M51 (NGC 5194). We find that the temporal and spectral evolution of the SN 1994I radio emission are well fit by a synchrotron self-absorption model and use this to estimate physical parameters. We compute a pre-explosion mass loss rate of $\dot{M}=3.0\times {{10}^{-5}}\;{{M}_{\odot }}$ yr⁻¹ for the progenitor, consistent with those observed from galactic Wolf–Rayet stars. Our model makes different assumptions for the dynamical model for the shockwave interaction than the model previously published by Weiler et al., but our $\dot{M}$ is consistent with theirs to within errors and assumptions. Drawing from a subset of the archival radio observations from the Very Large Array collected for the monitoring of SN 1994I, we conduct a pilot study to search for previously unidentified transients. Data were primarily taken at a frequency of 4.9 GHz and are logarithmic in cadence, enabling sensitivity to transients with variability timescales ranging from days to months. We find no new transient detections in 31 epochs of data, allowing us to place a $2\sigma$ upper limit of 17 deg⁻² for the source density of radio transients above 0.5 mJy ($L\;\gtrsim \;4\times {{10}^{25}}$ erg s⁻¹ Hz⁻¹ at the distance of M51). This study highlights the feasibility of utilizing archival high-cadence radio studies of SN host galaxies to place constraints on the radio transient rate as a function of luminosity in the local universe.

We present late-time near-infrared (NIR) spectral evolution, at 200–400 days, for the Type Ia supernova SN 2005df. The spectra show numerous strong emission features of [Co ii], [Co iii], and [Fe ii] throughout the 0.8–1.8 μm region. As the spectrum ages, the cobalt features fade as would be expected from the decay of ⁵⁶Co to ⁵⁶Fe. We show that the strong and isolated [Fe ii] emission line at $1.644\;\mu \rm{m}$ provides a unique tool to analyze NIR spectra of SNe Ia. Normalization of spectra to this line allows the separation of features produced by stable versus unstable isotopes of iron group elements. We develop a new method of determining the initial central density, ${\rho }_{c}$, and the magnetic field, B, of the white dwarf (WD) using the width of the $1.644\;\mu \rm{m}$ line. The line width (LW) is sensitive because of electron capture in the early stages of burning, which increases as a function of density. The sensitivity of the LW to B increases with time, and the effects of the magnetic field shift toward later times with decreasing ${\rho }_{c}$. Through comparison with spherical models, the initial central density for SN 2005df is measured as ${\rho }_{c}=0.9(\pm 0.2)\times {10}^{9}\;\rm{g}\;{\mathrm{cm}}^{-3}$, which corresponds to a WD close to the Chandrasekhar mass, with ${M}_{\mathrm{WD}}=1.31(\pm 0.03)\;{M}_{\odot}$ and systematic error less than $0.04\;{M}_{\odot}$. This error estimate is based on spherical models. We discuss the potential uncertainties due to multi-dimensional effects, mixing, and rotation. The latter two effects would increase the estimate of the WD mass. Within ${M}_{\mathrm{Ch}}$ explosions, however, the central density found for SN 2005df is very low for a H-accretor, possibly suggesting a helium star companion or a tidally disrupted WD companion. As an alternative, we suggest mixing of the central region. We find some support for high initial magnetic fields of strength ${10}^{6}\;\rm{G}$ for SN 2005df, however, $0\;\rm{G}$ cannot be ruled out because of noise in the spectra combined with low ${\rho }_{c}$. We discuss our findings in the context of mixing by Rayleigh–Taylor instabilities during deflagration burning and a wide variety of explosion scenarios. Observations strongly support a very limited amount of mixing during a deflagration phase and high central densities characteristic of a ${M}_{\mathrm{Ch}}$ WD.

We present deep near-infrared spectroscopic observations of 13 luminous $z\simeq 7$ Lyman break galaxies (LBGs) (${{M}_{{\rm UV}}}\simeq -21$) and a $z\simeq 9.6$ lensed LBG candidate, MACS1149-JD1, using the LBT/LUCI spectrograph in the multi-object mode and long-slit mode, respectively. The $z\sim 7$ galaxies are selected in one of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/WIDE survey observations, the UKIRT Infrared Deep Sky Survey Ultra Deep Survey field, and MACS1159-JD1 is selected from the Cluster Lensing And Supernova survey with Hubble survey observations. With ∼4–5 hr integrations, the LBT spectra are sensitive to Lyα emission, with rest-frame equivalent width greater than 55 Å (${\rm E}{{{\rm W}}_{0}}\gt 55$ Å) at $z\sim 7$ and 90 Å (${\rm E}{{{\rm W}}_{0}}\gt 90$ Å) at $z\sim 9.5$. No Lyα emission is observed in any of the $z\simeq 7$ LBGs. After correcting the spectroscopic incompleteness, our measurements place an upper limit on the Lyα emission fraction of ${{X}_{{\rm Ly}\alpha }}({\rm E}{{{\rm W}}_{0}}\gt 55\;{\rm {\ \mathrm{\mathring{\rm{A}}} }},z\simeq 7)\lt 9.8\%$ in luminous LBGs at $z\simeq 7$. This result is consistent with the lack of Lyα emission in $z\gt 7$ LBGs in previous studies. Together with other measurements of the Lyα emission fraction in LBGs at $z\simeq 7$, this study puts a strong constraint on the fraction of luminous $z\simeq 7$ LBGs with large EW Lyα, ${{X}_{{\rm Ly}\alpha }}({\rm E}{{{\rm W}}_{0}}\gt 55\;{\rm {\ \mathrm{\mathring{\rm{A}}} }},z\simeq 7)=2.6_{-2.6}^{+3.2}\%$. We estimate the expected Lyα emission fraction at $z\simeq 7$ by extrapolating the evolution of the fraction at low redshifts and find that the observed Lyα emission fraction is lower than the expected Lyα emission fraction at the 89% significance level, consistent with expectations if Lyα emission in $z\simeq 7$ LBGs has been suppressed by neutral hydrogen in the intergalactic medium or optically thick absorbers around the galaxies. We do not find any strong Lyα emission feature at the redshift range of $z\;\simeq$ 7.3–9.7 in the MACSJ1159-JD1 spectrum, either. This is consistent with the conclusion that Lyα emission in the galaxy has been highly suppressed.

We present the rest-frame optical spectral properties of 155 luminous quasars at 3.3 < z < 6.4 taken with the AKARI space telescope, including the first detection of the Hα emission line as far out as z ∼ 6. We extend the scaling relation between the rest-frame optical continuum and the line luminosity of active galactic nuclei (AGNs) to the high-luminosity, high-redshift regime that has rarely been probed before. Remarkably, we find that a single log-linear relation can be applied to the 5100 Å and Hα AGN luminosities over a wide range of luminosity (10⁴² < ${{L}_{5100}}$ < 10⁴⁷ ergs s⁻¹) or redshift (0 < z < 6), suggesting that the physical mechanism governing this relation is unchanged from z = 0 to 6, over five decades in luminosity. Similar scaling relations are found between the optical and the UV continuum luminosities or line widths. Applying the scaling relations to the Hβ black hole (BH) mass (${{M}_{{\rm BH}}}$) estimator of local AGNs, we derive the ${{M}_{{\rm BH}}}$ estimators based on the Hα, Mg ii, and C iv lines, finding that the UV-line-based masses are overall consistent with the Balmer-line-based, but with a large intrinsic scatter of 0.40 dex for the C iv estimates. Our 43 ${{M}_{{\rm BH}}}$ estimates from Hα confirm the existence of BHs as massive as ∼ ${{10}^{10}}\;{{M}_{\odot }}$ out to z ∼ 5 and provide a secure footing for previous results from Mg ii-line-based studies that a rapid ${{M}_{{\rm BH}}}$ growth has occurred in the early universe.

The ALESS survey has followed up on a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870 μm with the Atacama Large Millimeter Array (ALMA), allowing us to pinpoint the positions of sub-millimeter galaxies (SMGs) to ∼0.3 arcsec and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the magphys SED modeling code that is optimized to fit these ultraviolet-to-radio SEDs of $z\gt 1$ star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation, and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates (SFRs), and dust masses) for the ALESS SMGs. We find that the ALESS SMGs have median stellar mass ${M}_{*}=8.9\pm 0.1\times {10}^{10}\;{M}_{\odot }$, median SFR $=\;280\pm 70\;{M}_{\odot }\;{\mathrm{yr}}^{-1}$, median overall V-band dust attenuation ${A}_{V}=1.9\pm 0.2$ mag, median dust mass ${M}_{\mathrm{dust}}=(5.6\pm 1.0)\times {10}^{8}\;{M}_{\odot }$, and median average dust temperature ${T}_{\mathrm{dust}}\simeq 40$ K. We find that the average intrinsic SED of the ALESS SMGs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters (redshift, sub-millimeter flux, dust attenuation, and total infrared luminosity), and we provide a new set of SMG templates that can be used to interpret other SMG observations. To put the ALESS SMGs into context, we compare their stellar masses and SFRs with those of less actively star-forming galaxies at the same redshifts. We find that at $z\simeq 2$, about half of the SMGs lie above the star-forming main sequence (with SFRs three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. At higher redshifts ($z\simeq 3.5$), the SMGs tend to have higher SFRs and stellar masses, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third.

We report the discovery of rapid variations of a high-velocity C iv broad absorption line trough in the quasar SDSS J141007.74+541203.3. This object was intensively observed in 2014 as a part of the Sloan Digital Sky Survey Reverberation Mapping Project, during which 32 epochs of spectroscopy were obtained with the Baryon Oscillation Spectroscopic Survey spectrograph. We observe significant (>4σ) variability in the equivalent width (EW) of the broad (∼4000 km s⁻¹ wide) C iv trough on rest-frame timescales as short as 1.20 days (∼29 hr), the shortest broad absorption line variability timescale yet reported. The EW varied by ∼10% on these short timescales, and by about a factor of two over the duration of the campaign. We evaluate several potential causes of the variability, concluding that the most likely cause is a rapid response to changes in the incident ionizing continuum. If the outflow is at a radius where the recombination rate is higher than the ionization rate, the timescale of variability places a lower limit on the density of the absorbing gas of n_e ≳ 3.9 × 10⁵ cm⁻³. The broad absorption line variability characteristics of this quasar are consistent with those observed in previous studies of quasars, indicating that such short-term variability may in fact be common and thus can be used to learn about outflow characteristics and contributions to quasar/host-galaxy feedback scenarios.

We present polarization measurements of extragalactic radio sources observed during the cosmic microwave background polarization survey of the Q/U Imaging Experiment (QUIET), operating at 43 GHz (Q-band) and 95 GHz (W-band). We examine sources selected at 20 GHz from the public, >40 mJy catalog of the Australia Telescope (AT20G) survey. There are ∼480 such sources within QUIET's four low-foreground survey patches, including the nearby radio galaxies Centaurus A and Pictor A. The median error on our polarized flux density measurements is 30–40 mJy per Stokes parameter. At signal-to-noise ratio > 3 significance, we detect linear polarization for seven sources in Q-band and six in W-band; only 1.3 ± 1.1 detections per frequency band are expected by chance. For sources without a detection of polarized emission, we find that half of the sources have polarization amplitudes below 90 mJy (Q-band) and 106 mJy (W-band), at 95% confidence. Finally, we compare our polarization measurements to intensity and polarization measurements of the same sources from the literature. For the four sources with WMAP and Planck intensity measurements >1 Jy, the polarization fractions are above 1% in both QUIET bands. At high significance, we compute polarization fractions as much as 10%–20% for some sources, but the effects of source variability may cut that level in half for contemporaneous comparisons. Our results indicate that simple models—ones that scale a fixed polarization fraction with frequency—are inadequate to model the behavior of these sources and their contributions to polarization maps.

We cross-correlate foreground cleaned Planck Nominal cosmic microwave background (CMB) maps with two templates constructed from the Two-Micron All-Sky Redshift Survey of galaxies. The first template traces the large-scale filamentary distribution characteristic of the Warm–Hot Intergalactic Medium (WHIM) out to $\sim 90\;{{h}^{-1}}$ Mpc. The second preferentially traces the virialized gas in unresolved halos around galaxies. We find a marginal signal from the correlation of Planck data and the WHIM template with a signal to noise from 0.84 to 1.39 at the different Planck frequencies, and with a frequency dependence compatible with the thermal Sunyaev–Zel'dovich effect. When we restrict our analysis to the 60% of the sky outside the plane of the Galaxy and known point sources and galaxy clusters, the cross-correlation at zero lag is $0.064\pm 0.051\;\mu {\rm K}$. The correlation extends out to $\approx 6{}^\circ$, which at the median depth of our template corresponds to a physical length of $\sim 6{\rm --}8\;{{h}^{-1}}$ Mpc. On the same fraction of the sky, the cross-correlation of the CMB data with the second template is $\lt 0.17\;\mu {\rm K}$ (95% C.L.), providing no statistically significant evidence of a contribution from bound gas to the previous result. This limit translates into a physical constraint on the properties of the shock-heated WHIM of a log-normal model describing the weakly nonlinear density field. We find that our upper limit is compatible with a fraction of 45% of all baryons residing in filaments at overdensities ∼1–100 and with temperatures in the range ${{10}^{4.5}}{\rm --}{{10}^{7.5}}$ K, in agreement with the detection at redshift $z\sim 0.5$ of Van Waerbeke et al..

To understand the origin of Solar Energetic Particles (SEPs), we must study their injection time relative to other solar eruption manifestations. Traditionally the injection time is determined using the Velocity Dispersion Analysis (VDA) where a linear fit of the observed event onset times at 1 AU to the inverse velocities of SEPs is used to derive the injection time and path length of the first-arriving particles. VDA does not, however, take into account that the particles that produce a statistically observable onset at 1 AU have scattered in the interplanetary space. We use Monte Carlo test particle simulations of energetic protons to study the effect of particle scattering on the observable SEP event onset above pre-event background, and consequently on VDA results. We find that the VDA results are sensitive to the properties of the pre-event and event particle spectra as well as SEP injection and scattering parameters. In particular, a VDA-obtained path length that is close to the nominal Parker spiral length does not imply that the VDA injection time is correct. We study the delay to the observed onset caused by scattering of the particles and derive a simple estimate for the delay time by using the rate of intensity increase at the SEP onset as a parameter. We apply the correction to a magnetically well-connected SEP event of 2000 June 10, and show it to improve both the path length and injection time estimates, while also increasing the error limits to better reflect the inherent uncertainties of VDA.

We propose an in situ formation model for inverse-polarity solar prominences and demonstrate it using self-consistent 2.5 dimensional MHD simulations, including thermal conduction along magnetic fields and optically thin radiative cooling. The model enables us to form cool dense plasma clouds inside a flux rope by radiative condensation, which is regarded as an inverse-polarity prominence. Radiative condensation is triggered by changes in the magnetic topology, i.e., formation of the flux rope from the sheared arcade field, and by thermal imbalance due to the dense plasma trapped inside the flux rope. The flux rope is created by imposing converging and shearing motion on the arcade field. Either when the footpoint motion is in the anti-shearing direction or when heating is proportional to local density, the thermal state inside the flux rope becomes cooling-dominant, leading to radiative condensation. By controlling the temperature of condensation, we investigate the relationship between the temperature and density of prominences and derive a scaling formula for this relationship. This formula suggests that the proposed model reproduces the observed density of prominences, which is 10–100 times larger than the coronal density. Moreover, the time evolution of the extreme ultraviolet emission synthesized by combining our simulation results with the response function of the Solar Dynamics Observatory Atmospheric Imaging Assembly filters agrees with the observed temporal and spatial intensity shift among multi-wavelength extreme ultraviolet emission during in situ condensation.

We present results from a numerical forward model to evaluate one-dimensional reduced power spectral densities (PSDs) from arbitrary energy distributions in ${\boldsymbol{k}}$-space. In this model, we can separately calculate the diagonal elements of the spectral tensor for incompressible axisymmetric turbulence with vanishing helicity. Given a critically balanced turbulent cascade with ${{k}_{\parallel }}\sim k_{\bot }^{\alpha }$ and $\alpha \lt 1$, we explore the implications on the reduced PSD as a function of frequency. The spectra are obtained under the assumption of Taylor's hypothesis. We further investigate the functional dependence of the spectral index κ on the field-to-flow angle θ between plasma flow and background magnetic field from MHD to electron kinetic scales. We show that critically balanced turbulence asymptotically develops toward θ-independent spectra with a slope corresponding to the perpendicular cascade. This occurs at a transition frequency ${{f}_{2{\rm D}}}(L,\alpha ,\theta )$, which is analytically estimated and depends on outer scale L, critical balance exponent α, and field-to-flow angle θ. We discuss anisotropic damping terms acting on the ${\boldsymbol{k}}$-space distribution of energy and their effects on the PSD. Further, we show that the spectral anisotropies $\kappa (\theta )$ as found by Horbury et al. and Chen et al. in the solar wind are in accordance with a damped critically balanced cascade of kinetic Alfvén waves. We also model power spectra obtained by Papen et al. in Saturn's plasma sheet and find that the change of spectral indices inside $9\;{{R}_{s}}$ can be explained by damping on electron scales.

Fluctuations in a stellar system's gravitational field cause the orbits of stars to evolve. The resulting evolution of the system can be computed with the orbit-averaged Fokker–Planck equation once the diffusion tensor is known. We present the formalism that enables one to compute the diffusion tensor from a given source of noise in the gravitational field when the system's dynamical response to that noise is included. In the case of a cool stellar disk we are able to reduce the computation of the diffusion tensor to a one-dimensional integral. We implement this formula for a tapered Mestel disk that is exposed to shot noise and find that we are able to explain analytically the principal features of a numerical simulation of such a disk. In particular the formation of narrow ridges of enhanced density in action space is recovered. As the disk's value of Toomre's Q is reduced and the disk becomes more responsive, there is a transition from a regime of heating in the inner regions of the disk through the inner Lindblad resonance to one of radial migration of near-circular orbits via the corotation resonance in the intermediate regions of the disk. The formalism developed here provides the ideal framework in which to study the long-term evolution of all kinds of stellar disks.

We perform numerical experiments to study the shear dynamo problem where we look for the growth of a large-scale magnetic field due to non-helical stirring at small scales in a background linear shear flow in previously unexplored parameter regimes. We demonstrate the large-scale dynamo action in the limit where the fluid Reynolds number ($\operatorname{Re}$) is below unity while the magnetic Reynolds number (${\rm Rm}$) is above unity; the exponential growth rate scales linearly with shear, which is consistent with earlier numerical works. The limit of low $\operatorname{Re}$ is particularly interesting, as seeing the dynamo action in this limit would provide enough motivation for further theoretical investigations, which may focus attention on this analytically more tractable limit of $\operatorname{Re}\lt 1$ compared to the more formidable limit of $\operatorname{Re}\gt 1$. We also perform simulations in the regimes where (i) both ($\operatorname{Re}$, ${\rm Rm}$) < 1, and (ii) $\operatorname{Re}\gt 1$ and ${\rm Rm}\lt 1$, and compute all of the components of the turbulent transport coefficients (${{\alpha }_{ij}}$ and ${{\eta }_{ij}}$) using the test-field method. A reasonably good agreement is observed between our results and the results of earlier analytical works in similar parameter regimes.

The Local Leo Cold Cloud (LLCC, at a distance of 11–24 pc) was studied in its relation to the Local Hot Bubble (LHB) and the result suggested that much of the observed $1/4$ keV emission in that direction originates in front of the cloud. This placed a strong constraint on the distribution of X-ray emission within the LHB and called into question the assumption of a uniform distribution of X-ray emitting plasma within the Local Cavity. However, recent work has quantified the contribution of heliospheric solar wind charge exchange (SWCX) emission to the diffuse X-ray background measured by the ROSAT All-Sky Survey (RASS) at $1/4$ keV, and led to the consistency of pressure measurements between the LHB and the local cloud component of the complex of local interstellar clouds (CLICs) surrounding the Sun. In this paper we revisit the LLCC and improve the previous analysis by using higher resolution RASS data, a serendipitous ROSAT pointed observation, a rigorous treatment of the band-averaged X-ray absorption cross section, and models for the heliospheric and magnetospheric SWCX contributions. We find that the foreground emission to the cloud is in excess of the expected heliospheric (interplanetary plus near Earth) SWCX contribution but that it is marginally consistent with the range of possible LHB plasma path lengths between the LLCC and the CLICs given the currently understood plasma emissivity.

The North Galactic Pole Rift (NGPR) is one of the few distinct neutral hydrogen clouds at high Galactic latitudes that have well-defined distances. It is located at the edge of the Local Cavity (LC) and provides an important test case for understanding the Local Hot Bubble (LHB), the presumed location for the hot diffuse plasma responsible for much of the observed $1/4$ keV emission originating in the solar neighborhood. Using data from the ROSAT All-Sky Survey and the Planck reddening map, we find the path length within the LC (LHB plus Complex of Local Interstellar Clouds) to be 98 ± 27 pc, in excellent agreement with the distance to the NGPR of 98 ± 6 pc. In addition, we examine another 14 directions that are distributed over the sky where the LC wall is apparently optically thick at $1/4$ keV. We find that the data in these directions are also consistent with the LHB model and a uniform emissivity plasma filling most of the LC.

Polycyclic aromatic hydrocarbon (PAH) emission in the Spitzer/IRS spectral map of the northwest photon dominated region (PDR) in NGC 7023 is analyzed. Here, results from fitting the 5.2–14.5 μm spectrum at each pixel using exclusively PAH spectra from the NASA Ames PAH IR Spectroscopic Database (www.astrochem.org/pahdb/) and observed PAH band strength ratios, determined after isolating the PAH bands, are combined. This enables the first quantitative and spectrally consistent calibration of PAH charge proxies. Calibration is straightforward because the 6.2/11.2 μm PAH band strength ratio varies linearly with the ionized fraction (PAH ionization parameter) as determined from the intrinsic properties of the individual PAHs comprising the database. This, in turn, can be related to the local radiation field, electron density, and temperature. From these relations diagnostic templates are developed to deduce the PAH ionization fraction and astronomical environment in other objects. The commonly used 7.7/11.2 μm PAH band strength ratio fails as a charge proxy over a significant fraction of the nebula. The 11.2/12.7 μm PAH band strength ratio, commonly used as a PAH erosion indicator, is revealed to be a better tracer for PAH charge across NGC 7023. Attempting to calibrate the 12.7/11.2 μm PAH band strength ratio against the PAH hydrogen adjacency ratio (duo+trio)/solo is, unexpectedly, anti-correlated. This work both validates and extends the results from Paper I and Paper II.

We examine the relation between surface brightness, velocity dispersion, and size—the fundamental plane (FP)—for quiescent galaxies at intermediate redshifts in the COSMOS field. The COSMOS sample consists of ∼150 massive quiescent galaxies with an average velocity dispersion of σ ∼ 250 km s⁻¹ and redshifts between 0.2 < z < 0.8. More than half of the galaxies in the sample are compact. The COSMOS galaxies exhibit a tight relation (∼0.1 dex scatter) between surface brightness, velocity dispersion, and size. At a fixed combination of velocity dispersion and size, the COSMOS galaxies are brighter than galaxies in the local universe. These surface brightness offsets are correlated with the rest-frame g − z color and D_n4000 index; bluer galaxies and those with smaller D_n4000 indices have larger offsets. Stellar population synthesis models indicate that the massive COSMOS galaxies are younger and therefore brighter than similarly massive quiescent galaxies in the local universe. Passive evolution alone brings the massive compact quiescent (MCQ) COSMOS galaxies onto the local FP at z = 0. Therefore, evolution in size or velocity dispersion for MCQ galaxies since z ∼ 1 is constrained by the small scatter observed in the FP. We conclude that MCQ galaxies at z ≲ 1 are not a special class of objects but rather the tail of the mass and size distribution of the normal quiescent galaxy population.

We observed three massive subhalos in the Coma cluster with Suzaku. These subhalos, labeled "ID 1," "ID 2," and "ID 32," were detected with a weak-lensing survey using Subaru/Suprime-Cam, and are located at the projected distances of 1.4 r₅₀₀, 1.2 r₅₀₀, and 1.6 r₅₀₀ from the center of the Coma cluster, respectively. The subhalo "ID 1" has a compact X-ray excess emission close to the center of the weak-lensing mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The temperature of the emission is about 3 keV, which is slightly lower than that of the surrounding intracluster medium (ICM) and that expected for the temperature versus mass relation of clusters of galaxies. The subhalo "ID 32" shows an excess emission whose peak is shifted toward the opposite direction from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is also about 0.001, which is significantly smaller than regular galaxy groups. The temperature of the excess is about 0.5 keV and significantly lower than that of the surrounding ICM and far from the temperature versus mass relation of clusters. However, there is no significant excess X-ray emission in the "ID 2" subhalo. Assuming an infall velocity of about 2000 km s⁻¹, at the border of the excess X-ray emission, the ram pressures for "ID 1" and "ID 32" are comparable to the gravitational restoring force per area. We also studied the effect of the Kelvin–Helmholtz instability to strip the gas. Although we found X-ray clumps associated with the weak-lensing subhalos, their X-ray luminosities are much lower than the total ICM luminosity in the cluster outskirts.

The discovery of hypervelocity stars (HVSs) leaving our galaxy with speeds of nearly 10³ km s⁻¹ has provided strong evidence of the existence of a massive compact object at the galaxy's center. HVSs ejected via the disruption of stellar binaries can occasionally yield a star with ${{v}_{\infty }}\;\lesssim \;{{10}^{4}}$ km s⁻¹; here we show that this mechanism can be extended to massive black hole (MBH) mergers, where the secondary star is replaced by a MBH with mass ${{M}_{2}}\gtrsim {{10}^{5}}{{M}_{\odot }}$. We find that stars that are originally bound to the secondary MBH are frequently ejected with ${{v}_{\infty }}\gt {{10}^{4}}$ km s⁻¹, and occasionally with velocities ∼10⁵ km s⁻¹ (one third the speed of light). For this reason we refer to stars ejected from these systems as "semi-relativistic" hypervelocity stars (SHSs). Bound to no galaxy, the velocities of these stars are so great that they can cross a significant fraction of the observable universe in the time since their ejection (several Gpc). We demonstrate that if a significant fraction of MBH mergers undergoes a phase in which their orbital eccentricity is ≳0.5 and their periapse distance is tens of the primary's Schwarzschild radius, the space density of fast-moving (${{v}_{\infty }}\gt {{10}^{4}}$ km s⁻¹) SHSs may be as large as 10³ Mpc⁻³. Hundreds of SHSs will be giant stars that can be detected by future all-sky infrared surveys such as WFIRST or Euclid and proper motion surveys such as LSST, with spectroscopic follow-up being possible with the James Webb Space Telescope.

We measure the angular clustering of galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 in order to probe the spatial distribution of satellite galaxies within their dark matter halos. Specifically, we measure the angular correlation function on very small scales (7''–320'') in a range of luminosity threshold samples (absolute r-band magnitudes from −18 up to −21) that are constructed from the subset of SDSS that has been spectroscopically observed more than once (the so-called plate overlap region). We choose to measure angular clustering in this reduced survey footprint in order to minimize the effects of fiber collision incompleteness, which are otherwise substantial on these small scales, and we discuss the possible impact that fiber collisions have on our measurements. We model our clustering measurements using a fully numerical halo model that populates dark matter halos in N-body simulations to create realistic mock galaxy catalogs. The model has free parameters that specify both the number and spatial distribution of galaxies within their host halos. We adopt a flexible density profile for the spatial distribution of satellite galaxies that is similar to the dark matter Navarro–Frenk–White (NFW) profile, except that the inner slope is allowed to vary. We find that the angular clustering of our most luminous samples (${{M}_{r}}$ < −20 and −21) suggests that luminous satellite galaxies have substantially steeper inner density profiles than NFW. Lower-luminosity samples are less constraining, however, and are consistent with satellite galaxies having shallow density profiles. Our results confirm the findings of Watson et al. while using different clustering measurements and modeling methodology.

We present nearly simultaneous Chandra and NuSTAR observations of two actively star-forming galaxies within 50 Mpc: NGC 3256 and NGC 3310. Both galaxies are significantly detected by both Chandra and NuSTAR, which together provide the first-ever spectra of these two galaxies spanning 0.3–30 keV. The X-ray emission from both galaxies is spatially resolved by Chandra; we find that hot gas dominates the E < 1–3 keV emission while ultraluminous X-ray sources (ULXs) provide majority contributions to the emission at E > 1–3 keV. The NuSTAR galaxy-wide spectra of both galaxies follow steep power-law distributions with Γ ≈ 2.6 at E > 5–7 keV. Using new and archival Chandra data, we search for signatures of heavily obscured or low luminosity active galactic nuclei (AGNs). We find that both NGC 3256 and NGC 3310 have X-ray detected sources coincident with nuclear regions; however, the steep NuSTAR spectra of both galaxies restricts these sources to be either low luminosity AGNs (L_{2−10 keV}/L_Edd ≲ 10⁻⁵) or non-AGNs in nature (e.g., ULXs or crowded X-ray sources that reach L_{2−10 keV} ∼ 10⁴⁰ erg s⁻¹ cannot be ruled out). Combining our constraints on the 0.3–30 keV spectra of NGC 3256 and NGC 3310 with equivalent measurements for nearby star-forming galaxies M83 and NGC 253, we analyze the star formation rate (SFR) normalized spectra of these starburst galaxies. The spectra of all four galaxies show sharply declining power-law slopes at energies above 3–6 keV primarily due to ULX populations. Our observations therefore constrain the average spectral shape of galaxy-wide populations of luminous accreting binaries (i.e., ULXs). Interestingly, despite a completely different galaxy sample selection, emphasizing here a range of SFRs and stellar masses, these properties are similar to those of super-Eddington accreting ULXs that have been studied individually in a targeted NuSTAR ULX program. We also find that NGC 3310 exhibits a factor of ≈3–10 elevation of X-ray emission over the other star-forming galaxies due to a corresponding overabundance of ULXs. We argue that the excess of ULXs in NGC 3310 is most likely explained by the relatively low metallicity of the young stellar population in this galaxy, a property that is expected to produce an excess of luminous X-ray binaries for a given SFR.

We describe a complete volume limited sample of nearby active galaxies selected by their 14–195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We also describe a complementary sample of inactive galaxies, selected to match the host galaxy properties. The active sample appears to have no bias in terms of active galactic nucleus (AGN) type, the only difference being the neutral absorbing column, which is two orders of magnitude greater for the Seyfert 2s. In the luminosity range spanned by the sample, ${\rm log} {{L}_{14-195\,{\rm keV}}}[{\rm erg}\;{{{\rm s}}^{-1}}]=42.4$–43.7, the optically obscured and X-ray absorbed fractions are 50%–65%. The similarity of these fractions to more distant spectroscopic AGN samples, although over a limited luminosity range, suggests that the torus does not strongly evolve with redshift. Our sample confirms that X-ray unabsorbed Seyfert 2s are rare, comprising not more than a few percent of the Seyfert 2 population. At higher luminosities, the optically obscured fraction decreases (as expected for the increasing dust sublimation radius), but the X-ray absorbed fraction changes little. We argue that the cold X-ray absorption in these Seyfert 1s can be accounted for by neutral gas in clouds that also contribute to the broad-line region (BLR) emission, and suggest that a geometrically thick neutral gas torus co-exists with the BLR and bridges the gap to the dusty torus.

We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 171 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Significant correlated variability is found in the continuum and broad emission lines, with amplitudes ranging from ∼30% to a factor of two in the emission lines and a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He ii$\lambda 1640$ lagging behind the continuum by ∼2.5 days and Lyα$\lambda 1215$, C iv$\lambda 1550$, and Si iv$\lambda 1400$ lagging by ∼5–6 days. The relationship between the continuum and emission lines is complex. In particular, during the second half of the campaign, all emission-line lags increased by a factor of 1.3–2 and differences appear in the detailed structure of the continuum and emission-line light curves. Velocity-resolved cross-correlation analysis shows coherent structure in lag versus line of sight velocity for the emission lines; the high-velocity wings of C iv respond to continuum variations more rapidly than the line core, probably indicating higher velocity broad-line region clouds at smaller distances from the central engine. The velocity-dependent response of Lyα, however, is more complex and will require further analysis.

Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (${{r}_{{\rm max} }}=0.57-0.90$) and the clearest measurement to date of interband lags. These lags are well-fit by a $\tau \propto {{{\lambda }}^{4/3}}$ wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of $\sim 0.35\pm 0.05$ lt-day at 1367 Å, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (${{r}_{{\rm max} }}\lt 0.45$) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.

The high velocity dispersion compact cloud CO–0.30–0.07 is a peculiar molecular clump discovered in the central molecular zone of the Milky Way, which is characterized by its extremely broad velocity emissions ($\sim 145\;{\rm km}\;{{{\rm s}}^{-1}}$) despite the absence of internal energy sources. We present new interferometric maps of the cloud in multiple molecular lines in frequency ranges of 265–269 GHz and 276–280 GHz obtained using the Submillimeter Array, along with the single-dish images previously obtained with the ASTE 10 m telescope. The data show that the characteristic broad velocity emissions are predominantly confined in two parallel ridges running through the cloud center. The central ridges are tightly anticorrelated with each other in both space and velocity, thereby sharply dividing the entire cloud into two distinct velocity components (+15 and +55 km s⁻¹). This morphology is consistent with a model in which the two velocity components collide with a relative velocity of 40 ${\rm km}\;{{{\rm s}}^{-1}}$ at the interface defined by the central ridges, although an alternative explanation with a highly inclined expanding-ring model is yet to be fully invalidated. We have also unexpectedly detected several compact clumps ($\lesssim 0.1$ pc in radius) likely formed by shock compression. The clumps have several features in common with typical star-forming clouds: high densities (${{10}^{6.5{\rm --}7.5}}\;{\rm c}{{{\rm m}}^{-3}}$), rich abundances of hot-core-type molecular species, and relatively narrow velocity widths apparently decoupled from the furious turbulence dominating the cloud. The cloud CO–0.30–0.07 is possibly at an early phase of star formation activity triggered by the shock impact.

We study the linear and nonlinear evolution of the tearing instability on thin current sheets by means of two-dimensional numerical simulations, within the framework of compressible, resistive MHD. In particular we analyze the behavior of current sheets whose inverse aspect ratio scales with the Lundquist number S as ${{S}^{-1/3}}$. This scaling has been recently recognized to yield the threshold separating fast, ideal reconnection, with an evolution and growth that are independent of S provided this is high enough, as it should be natural having the ideal case as a limit for $S\to \infty$. Our simulations confirm that the tearing instability growth rate can be as fast as $\gamma \approx 0.6\;{{\tau }_{{\rm A}}}^{-1}$, where ${{\tau }_{{\rm A}}}$ is the ideal Alfvénic time set by the macroscopic scales, for our least diffusive case with $S={{10}^{7}}$. The expected instability dispersion relation and eigenmodes are also retrieved in the linear regime, for the values of S explored here. Moreover, in the nonlinear stage of the simulations we observe secondary events obeying the same critical scaling with S, here calculated on the local, much smaller lengths, leading to increasingly faster reconnection. These findings strongly support the idea that in a fully dynamic regime, as soon as current sheets develop, thin, and reach this critical threshold in their aspect ratio, the tearing mode is able to trigger plasmoid formation and reconnection on the local (ideal) Alfvénic timescales, as required to explain the explosive flaring activity often observed in solar and astrophysical plasmas.

We present observational evidence of compressible MHD wave modes propagating from the solar photosphere through to the base of the transition region in a solar magnetic pore. High cadence images were obtained simultaneously across four wavelength bands using the Dunn Solar Telescope. Employing Fourier and wavelet techniques, sausage-mode oscillations displaying significant power were detected in both intensity and area fluctuations. The intensity and area fluctuations exhibit a range of periods from 181 to 412 s, with an average period ∼290 s, consistent with the global p-mode spectrum. Intensity and area oscillations present in adjacent bandpasses were found to be out of phase with one another, displaying phase angles of 612, 582, and 1597 between the 4170 Å continuum–G-band, G-band–Na i D₁, and Na i D₁–Ca ii K heights, respectively, reiterating the presence of upwardly propagating sausage-mode waves. A phase relationship of ∼0° between same-bandpass emission and area perturbations of the pore best categorizes the waves as belonging to the "slow" regime of a dispersion diagram. Theoretical calculations reveal that the waves are surface modes, with initial photospheric energies in excess of 35,000 W m⁻². The wave energetics indicate a substantial decrease in energy with atmospheric height, confirming that magnetic pores are able to transport waves that exhibit appreciable energy damping, which may release considerable energy into the local chromospheric plasma.

We present a kinematic analysis of the globular cluster (GC) systems and diffuse stellar light of four intermediate luminosity (sub-L*) early-type galaxies in the Virgo cluster based on Gemini Multi-Object Spectrographs (GMOS) data. Our galaxy sample is fainter ($-23.8\lt {{M}_{K}}\lt -22.7$) than most previous studies, nearly doubling the number of galaxies in this magnitude range that now have GC kinematics. The data for the diffuse light extends to 4R_e, and the data for the GCs reaches 8–12R_e. We find that the kinematics in these outer regions are all different despite the fact that these four galaxies have similar photometric properties, and are uniformly classified as "fast rotators" from their stellar kinematics within 1R_e. The GC systems exhibit a wide range of kinematic morphology. The rotation axis and amplitude can change between the inner and outer regions, including a case of counter-rotation. This difference shows the importance of wide-field kinematic studies, and shows that stellar and GC kinematics can change significantly as one moves beyond the inner regions of galaxies. Moreover, the kinematics of the GC systems can differ from that of the stars, suggesting that the formation of the two populations are also distinct.

We present an analytical model for light echoes (LEs) coming from circumstellar material (CSM) around Type Ia Supernovae (SNe Ia). Using this model we find two spectral signatures at 4100 Å and 6200 Å that are useful to identify LEs during the Lira law phase (between 35 and 80 days after maximum light) coming from nearby CSM at distances of 0.01–0.25 pc. We analyze a sample of 89 SNe Ia divided into two groups according to their $B-V$ decline rate during the Lira law phase, and search for LEs from CSM interaction in the group of SNe with steeper slopes by comparing their spectra with our LE model. We find that a model with LEs + pure extinction from interstellar material (ISM) fits the observed spectra better than a pure ISM extinction model that is constant in time, but we find that a decreasing extinction alone explains the observations better without the need of LEs, possibly implying dust sublimation due to the radiation from the SN.

Massive stars are usually found in binaries, and binaries with periods less than 10 days may have a preference for near equal component masses ("twins"). In this paper we investigate the evolution of massive twin binaries all the way to contact and the possibility that these systems can be progenitors of double neutron star binaries. The small orbital separations of observed double neutron star binaries suggest that the progenitor systems underwent a common envelope phase at least once during their evolution. Bethe & Brown proposed that massive binary twins will undergo a common envelope evolution while both components are ascending the red giant branch (RGB) or asymptotic giant branch (AGB) simultaneously, also known as double-core evolution. Using models generated from the stellar evolution code EZ (evolve zero-age main sequence), we determine the range of mass ratios resulting in a contact binary with both components simultaneously ascending the RGB or AGB as a function of the difference in birth times, Δτ. We find that, even for a generous Δτ = 5 Myr, the minimum mass ratio ${{q}_{{\rm min} }}=0.933$ for an $8\;{{M}_{\odot }}$ primary and increases for larger mass primaries. We use a smoothed particle hydrodynamics code, StarSmasher, to study specifically the evolution of q = 1 common envelope systems as a function of initial component mass, age, and orbital separation. We also consider a q = 0.997 system to test the effect of relaxing the constraint of strictly identical components. We find the dynamical stability limit, the largest orbital separation where the binary becomes dynamically unstable, as a function of the component mass and age. Finally, we calculate the efficiency of ejecting matter during the inspiral phase to extrapolate the properties of the remnant binary from our numerical results, assuming the common envelope is completely ejected. We find that for the nominal core masses, there is a minimum orbital separation for a given component mass such that the helium cores survive common envelope evolution in a tightly bound binary and are viable progenitors for double neutron stars.

Using data from the DEEP2 galaxy redshift survey and the All Wavelength Extended Groth Strip International Survey we obtain stacked X-ray maps of galaxies at $0.7\leqslant z\leqslant 1.0$ as a function of stellar mass. We compute the total X-ray counts of these galaxies and show that in the soft band (0.5–2 kev) there exists a significant correlation between galaxy X-ray counts and stellar mass at these redshifts. The best-fit relation between X-ray counts and stellar mass can be characterized by a power law with a slope of 0.58 ± 0.1. We do not find any correlation between stellar mass and X-ray luminosities in the hard (2–7 kev) and ultra-hard (4–7 kev) bands. The derived hardness ratios of our galaxies suggest that the X-ray emission is degenerate between two spectral models, namely point-like power-law emission and extended plasma emission in the interstellar medium. This is similar to what has been observed in low redshift galaxies. Using a simple spectral model where half of the emission comes from power-law sources and the other half from the extended hot halo we derive the X-ray luminosities of our galaxies. The soft X-ray luminosities of our galaxies lie in the range 10³⁹–$8\times {{10}^{40}}$ erg s⁻¹. Dividing our galaxy sample by the criteria $U-B\gt 1$, we find no evidence that our results for X-ray scaling relations depend on optical color.

The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars in the circumstellar Habitable Zone for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early-Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present-day levels at 2.0 Gyr ago, 0.8 Gyr ago, and modern Earth. In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth–Sun levels. A pre-biotic Earth orbiting GJ 581 (M3.5 V) receives 300 times less biologically effective radiation, about 2 times modern Earth–Sun levels. The UV fluxes calculated here provide a grid of model UV environments during the evolution of an Earth-like planet orbiting a range of stars. These models can be used as inputs into photo-biological experiments and for pre-biotic chemistry and early life evolution experiments.

We discuss here two unusual increases of cosmic ray intensity that were observed by V1 in the last 1.1 AU before it crossed the heliopause in 2012 August, at 121.5 AU. These two increases are roughly similar in amplitude and result in a total increase in ∼1 GV cosmic ray nuclei of over 50% and 0.01 GV electrons of a factor ∼2. During the first increase the changes in the B field are small. After the first increase the B field changes become large and during the second increase the B field variations and cosmic ray changes are correlated to within ± one day. During these time intervals, the rigidity dependence of the increases of GCR H and He nuclei from 100–600 MeV/nuc resemble those used to describe the solar modulation near the Earth during a large transient decrease but the ratio between the intensity changes of H, He, and electrons are different. The magnitude of these increases at Voyager is ∼1/3 of the modulation that is required to produce the total modulation of protons, helium nuclei, and electrons between the local interstellar intensities and those observed at the Earth at the 2009 sunspot minima. This may imply that a significant part of the residual solar modulation at times of sunspot minima occurs near the heliopause itself.

We present the first investigation of Th abundances in solar twins and analogues to understand the possible range of this radioactive element and its effect on rocky planet interior dynamics and potential habitability. The abundances of the radioactive elements Th and U are key components of a planet's energy budget, making up 30%–50% of the Earth's. Radiogenic heat drives interior mantle convection and surface plate tectonics, which sustains a deep carbon and water cycle and thereby aides in creating Earth's habitable surface. Unlike other heat sources that are dependent on the planet's specific formation history, the radiogenic heat budget is directly related to the mantle concentration of these nuclides. As a refractory element, the stellar abundance of Th is faithfully reflected in the terrestrial planet's concentration. We find that log ${{\epsilon }_{{\rm Th}}}$ varies from 59% to 251% that of solar, suggesting extrasolar planetary systems may possess a greater energy budget with which to support surface to interior dynamics and thus increase their likelihood to be habitable compared to our solar system.

We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M_⊙ and is most likely a white dwarf (WD). Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities e < 0.001. However, four recently discovered binary MSPs have orbits with 0. 027 < e < 0.44; PSR J1950+2414 is the fifth such system to be discovered. The upper limits for its intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities are incompatible with the predictions of the standard recycling scenario: something unusual happened during their evolution. Proposed scenarios are (a) initial evolution of the pulsar in a triple system which became dynamically unstable, (b) origin in an exchange encounter in an environment with high stellar density, (c) rotationally delayed accretion-induced collapse of a super-Chandrasekhar WD, and (d) dynamical interaction of the binary with a circumbinary disk. We compare the properties of all five known eccentric MSPs with the predictions of these formation channels. Future measurements of the masses and proper motion might allow us to firmly exclude some of the proposed formation scenarios.

Using only physical mechanisms, i.e., 3D magnetohydrodynamics (MHD) with no phenomenological viscosity, we have simulated the dynamics of a moderately thin accretion disk subject to torques whose radial scaling mimics those produced by lowest-order post-Newtonian gravitomagnetism. In this simulation, we have shown how, in the presence of MHD turbulence, a time-steady transition can be achieved between an inner disk region aligned with the equatorial plane of the central mass's spin and an outer region orbiting in a different plane. The position of the equilibrium orientation transition is determined by a balance between gravitomagnetic torque and warp-induced inward mixing of misaligned angular momentum from the outer disk. If the mixing is interpreted in terms of diffusive transport, the implied diffusion coefficient is ≃(0.6–0.8)$c_{{\rm s}}^{2}/{\Omega }$ for sound speed c_s and orbital frequency Ω. This calibration permits estimation of the orientation transition's equilibrium location given the central mass, its spin parameter, and the disk's surface density and scaleheight profiles. However, the alignment front overshoots before settling into an equilibrium, signaling that a diffusive model does not fully represent the time-dependent properties of alignment fronts under these conditions. Because the precessional torque on the disk at the alignment front is always comparable to the rate at which misaligned angular momentum is brought inward to the front by warp-driven radial motions, no break forms between the inner and outer portions of the disk in our simulation. Our results also raise questions about the applicability to MHD warped disks of the traditional distinction between "bending wave" and "diffusive" regimes.

The proximity profile in the spectra of $z\approx 3$ quasars, where fluxes extend blueward of the He ii Lyα wavelength 304 (1+z) Å, is one of the most important spectral features in the study of the intergalactic medium (IGM). Based on the Hubble Space Telescope spectra of 24 He ii quasars, we find that the majority of them display a proximity profile, corresponding to an ionization radius as large as 20 Mpc in the source's rest frame. In comparison with those in the H i spectra of the quasars at z ≈ 6, the He ii proximity effect is more prominent and is observed over a considerably longer period of reionization. The He ii proximity zone sizes decrease at higher redshifts, particularly at $z\gt 3.3$. This trend is similar to that for H i, signaling an onset of He ii reionization at $z\gtrsim 4$. For quasar SDSS1253+6817 (z = 3.48), the He ii absorption trough displays a gradual decline and serves as a good case for modeling the He ii reionization. To model such a broad profile requires a quasar radiation field whose energy distribution between 4 and 1 Rydberg is considerably harder than normally assumed. The UV continuum of this quasar is indeed exceptionally steep, and the He ii ionization level in the quasar vicinity is higher than the average level in the IGM. These results are evidence that a very hard EUV continuum from this quasar produces a large ionized zone around it. Distinct exceptions are the two brightest He ii quasars at z ≈ 2.8, for which no significant proximity profile is present, probably implying that they are very young.

We study the effects of planetary late migration on the gas giants' obliquities. We consider the planetary instability models from Nesvorný and Morbidelli, in which the obliquities of Jupiter and Saturn can be excited when spin–orbit resonances occur. The most notable resonances occur when the s₇ and s₈ frequencies, changing as a result of planetary migration, become commensurate with the precession frequencies of Jupiter's and Saturn's spin vectors. We show that Jupiter may have obtained its present obliquity by crossing of the s₈ resonance. This would set strict constraints on the character of migration during the early stage. Additional effects on Jupiter's obliquity are expected during the last gasp of migration when the s₇ resonance was approached. The magnitude of these effects depends on the precise value of the Jupiter's precession constant. Saturn's large obliquity was likely excited by capture into the s₈ resonance. This probably happened during the late stage of planetary migration when the evolution of the s₈ frequency was very slow, and the conditions for capture into the spin–orbit resonance with s₈ were satisfied. However, whether or not Saturn is in the spin–orbit resonance with s₈ at the present time is not clear because the existing observations of Saturn's spin precession and internal structure models have significant uncertainties.