Table of contents

We present three giant stars from the ongoing Penn State–Toruń Planet Search with the Hobby–Eberly Telescope, which exhibit radial velocity (RV) variations that point to the presence of planetary-mass companions around them. ${\rm BD}+49\;828$ is a $M=1.52\pm 0.22\;{{M}_{\odot }}$ K0 giant with a $m\;{\rm sin} \;i=1.6_{-0.2}^{+0.4}\;{{M}_{J}}$ minimum mass companion in a = 4.2^+0.32_−0.2 AU (2590⁺³⁰⁰₋₁₈₀d), e = 0.35^+0.24_−0.10 orbit. HD 95127, a ${\rm log} L/{{L}_{\odot }}=2.28\pm 0.38$, $R=20\pm 9\;{{R}_{\odot }}$, $M=1.20\pm 0.22\;{{M}_{\odot }}$ K0 giant, has a $m\;{\rm sin} \;i$ = $5.01_{-0.44}^{+0.61}\;{{M}_{J}}$ minimum mass companion in a = 1.28^+0.01_−0.01 AU (482⁺⁵₋₅d), e = 0.11^+0.15_−0.06 orbit. Finally, HD 216536 is a $M=1.36\pm 0.38\;{{M}_{\odot }}$ K0 giant with a $m{\rm sin} i=1.47_{-0.12}^{+0.20}\;{{M}_{J}}$ minimum mass companion in $a=0.609_{-0.002}^{+0.002}$ AU ($148.6_{-0.7}^{+0.7}$d), e = 0.38^+0.12_−0.10 orbit. Both HD 95127 b and HD 216536 b in their compact orbits are very close to the engulfment zone and hence prone to ingestion in the near future. BD+49 828 b is among the longest-period planets detected with the RV technique until now and it will remain unaffected by stellar evolution up to a very late stage of its host. We discuss general properties of planetary systems around evolved stars and planet survivability using existing data on exoplanets in more detail.

Active galactic nuclei (AGNs) are well-known to exhibit flux variability across a wide range of wavelength regimes, but the precise origin of the variability at different wavelengths remains unclear. To investigate the relatively unexplored near-IR (NIR) variability of the most luminous AGNs, we conduct a search for variability using well sampled JHK_s-band light curves from the Two Micron All Sky Survey (2MASS) calibration fields. Our sample includes 27 known quasars with an average of 924 epochs of observation over three years, as well as one spectroscopically confirmed blazar (SDSS J14584479+3720215) with 1972 epochs of data. This is the best-sampled NIR photometric blazar light curve to date, and it exhibits correlated, stochastic variability that we characterize with continuous auto-regressive moving average (CARMA) models. None of the other 26 known quasars had detectable variability in the 2MASS bands above the photometric uncertainty. A blind search of the 2MASS calibration field light curves for active galactic nucleus (AGN) candidates based on fitting CARMA(1,0) models (damped-random walk) uncovered only seven candidates. All seven were young stellar objects within the ρ Ophiuchus star forming region, five with previous X-ray detections. A significant γ-ray detection (5σ) for the known blazar using 4.5 yr of Fermi photon data is also found. We suggest that strong NIR variability of blazars, such as seen for SDSS J14584479+3720215, can be used as an efficient method of identifying previously unidentified γ-ray blazars, with low contamination from other AGNs.

We study the kinematics of ridge lines on the parsec-scale jet of the active galactic nucleus BL Lacertae. We show that the ridge lines display transverse patterns that move superluminally downstream, and that the moving patterns are analogous to waves on a whip. Their apparent speeds β_app (units of c) range from 3.9 to 13.5, corresponding to ${\beta }_{\mathrm{wave}}^{\mathrm{gal}}=0.981-0.998$ in the galaxy frame. We show that the magnetic field in the jet is well ordered with a strong transverse component, and assume that it is helical and that the transverse patterns are Alfvén waves propagating downstream on the longitudinal component of the magnetic field. The wave-induced transverse speed of the jet is non-relativistic (${\beta }_{\mathrm{tr}}^{\mathrm{gal}}\lesssim 0.09$). In 2010 the wave activity subsided and the jet then displayed a mild wiggle that had a complex oscillatory behavior. The Alfvén waves appear to be excited by changes in the position angle of the recollimation shock, in analogy to exciting a wave on a whip by shaking the handle. A simple model of the system with plasma sound speed β_s = 0.3 and apparent speed of a slow MHD wave β_app, S = 4 yields Lorentz factor of the beam Γ_beam ∼ 4.5, pitch angle of the helix (in the beam frame) α ∼ 67°, Alfvén speed β_A ∼ 0.64, and magnetosonic Mach number M_ms ∼ 4.7. This describes a plasma in which the magnetic field is dominant and in a rather tight helix, and Alfvén waves are responsible for the moving transverse patterns.

We study the dependence of quasar clustering on quasar luminosity and black hole mass by measuring the angular overdensity of photometrically selected galaxies imaged by the Wide-field Infrared Survey Explorer (WISE) about z ∼ 0.8 quasars from SDSS. By measuring the quasar–galaxy cross-correlation function and using photometrically selected galaxies, we achieve a higher density of tracer objects and a more sensitive detection of clustering than measurements of the quasar autocorrelation function. We test models of quasar formation and evolution by measuring the luminosity dependence of clustering amplitude. We find a significant overdensity of WISE galaxies about z ∼ 0.8 quasars at 0.2–6.4 h⁻¹ Mpc in projected comoving separation. We find no appreciable increase in clustering amplitude with quasar luminosity across a decade in luminosity, and a power-law fit between luminosity and clustering amplitude gives an exponent of −0.01 ± 0.06 (1 σ error). We also fail to find a significant relationship between clustering amplitude and black hole mass, although our dynamic range in true mass is suppressed due to the large uncertainties in virial black hole mass estimates. Our results indicate that a small range in host dark matter halo mass maps to a large range in quasar luminosity.

We explore the connection between the central supermassive black holes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well-established SMBH mass–bulge velocity dispersion relation. Using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution. We believe that our approach will provide a more direct probe of the SMBH and the dark matter halo connection. We find that the correlation between the mass of SMBHs and the circular velocities of the host galaxies is extremely weak, leading us to state the dark matter halo may not play a major role in regulating the black hole growth in the present Universe.

We present new Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet (far-UV) spectroscopy and Keck Echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ULIRGs), a rare population of local galaxies experiencing massive gas inflows, extreme starbursts, and prominent outflows. We detect Lyα emission from eight ULIRGs and the companion to IRAS09583+4714. In contrast to the P Cygni profiles often seen in galaxy spectra, the Lyα profiles exhibit prominent, blueshifted emission out to Doppler shifts exceeding −1000 km s⁻¹ in three H ii-dominated and two AGN-dominated ULIRGs. To better understand the role of resonance scattering in shaping the Lyα line profiles, we directly compare them to non-resonant emission lines in optical spectra. We find that the line wings are already present in the intrinsic nebular spectra, and scattering merely enhances the wings relative to the line core. The Lyα attenuation (as measured in the COS aperture) ranges from that of the far-UV continuum to over 100 times more. A simple radiative transfer model suggests the Lyα photons escape through cavities which have low column densities of neutral hydrogen and become optically thin to the Lyman continuum in the most advanced mergers. We show that the properties of the highly blueshifted line wings on the Lyα and optical emission-line profiles are consistent with emission from clumps of gas condensing out of a fast, hot wind. The luminosity of the Lyα emission increases nonlinearly with the ULIRG bolometric luminosity and represents about 0.1–1% of the radiative cooling from the hot winds in the H ii-dominated ULIRGs.

Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however, that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al., we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities ≳200 km s⁻¹ for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction timescales are increased by a factor of ∼2 compared to those of Jones et al., who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of ∼3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of ∼2–3 Gyr. These increases, while not able to resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step toward understanding the origin and evolution of dust in the ISM.

Exoplanetary systems closest to the Sun, with the brightest host stars, provide the most favorable opportunities for characterization studies of the host star and their planet(s). The Transit Ephemeris Refinement and Monitoring Survey uses both new radial velocity (RV) measurements and photometry in order to greatly improve planetary orbit uncertainties and the fundamental properties of the star, in this case HD 130322. The only companion, HD 130322b, orbits in a relatively circular orbit, e = 0.029 every ∼10.7 days. We have compiled RV measurements from multiple sources, including 12 unpublished from the Keck I telescope, over the course of ∼14 yr and have reduced the uncertainty in the transit midpoint to ∼2 hr. The transit probability for the b-companion is 4.7%, where ${{M}_{p}}{\rm sin} i=1.15\;{{M}_{J}}$ and a = 0.0925 AU. In this paper, we compile photometric data from the T11 0.8 m Automated Photoelectric Telescope at Fairborn Observatory taken over ∼14 yr, including the constrained transit window, which results in a dispositive null result for both full transit exclusion of HD 130322b to a depth of 0.017 mag and grazing transit exclusion to a depth of ∼0.001 mag. Our analysis of the starspot activity via the photometric data reveals a highly accurate stellar rotation period: 26.53 ± 0.70 days. In addition, the brightness of the host with respect to the comparison stars is anti-correlated with the Ca ii H and K indices, typical for a young solar-type star.

We present new observations of four closely spaced near-ultraviolet (NUV) transits of the hot Jupiter-like exoplanet WASP-12b using Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS), significantly increasing the phase resolution of the observed NUV light curve relative to previous observations, while minimizing the temporal variation of the system. We observe significant excess NUV absorption during the transit, with mean normalized in-transit fluxes of ${{F}_{{\rm norm}}}\simeq 0.97$, i.e., $\simeq$2–5σ deeper than the optical transit level of $\simeq 0.986$ for a uniform stellar disk (the exact confidence level depending on the normalization method used). We further observe an asymmetric transit shape, such that the post-conjunction fluxes are overall $\simeq$2–3σ higher than pre-conjunction values, and characterized by rapid variations in count rate between the pre-conjunction and out-of-transit levels. We do not find evidence for an early ingress to the NUV transit as suggested by earlier HST observations. However, we show that the NUV count rate observed prior to the optical transit is highly variable, but overall $\simeq$2.2–3.0σ below the post-transit values and comparable in depth to the optical transit, possibly forming a variable region of NUV absorption from at least phase $\phi \simeq 0.83$, limited by the data coverage.

Simultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as the origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find that in this scenario, X-ray flares can be produced by a late-time relativistic (Γ > 50) outflow at radii R ∼ 10¹³–10¹⁴ cm. This conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.

We build a Spitzer IRAC-complete catalog of objects complementing the K_s-band selected UltraVISTA catalog with objects detected in IRAC only. To identify massive (${\rm log} ({{M}_{*}}/{{M}_{\odot }})\gt 11$) galaxies at $4\lt z\lt 7$, we consider the systematic effects on photometric redshift measurements from the introduction of an old and dusty template and of a bayesian prior on luminosity, as well as the systematic effects from different star formation histories (SFHs) and from nebular emission lines in estimated stellar population properties. Our results are most affected by the luminosity prior, while nebular lines and SFHs marginally increase the measurement dispersion; the samples include 52 to 382 galaxies, depending on the adopted configuration. Using these results we investigate, for the first time, the evolution of the massive end of the stellar mass functions (SMFs) at $4\lt z\lt 7$. Given the rarity of massive galaxies at these redshifts, cosmic variance and Poisson noise dominate the total error budget. The SMFs obtained excluding the luminosity prior show no evolution from $z\sim 6.5$ to $z\sim 3.5$, indicating that massive galaxies could already be present at early epochs. The luminosity prior reduces the number of $z\gt 4$ massive galaxies by 83%, implying a rapid growth of massive galaxies in the first 1.5 Gyr of cosmic history. The stellar-mass complete sample includes one candidate of a very massive (${\rm log} ({{M}_{*}}/{{M}_{\odot }})\sim 11.5$), quiescent galaxy at $z\sim 5.4$ with MIPS $24\;\mu {\rm m}$ detection, suggesting the presence of an obscured active galactic nucleus. Finally, we show that the observed number of $4\lt z\lt 7$ massive galaxies matches the number of massive galaxies at $3\lt z\lt 6$ predicted by current galaxy formation models.

We present strontium, barium, carbon, and silicon isotopic compositions of 61 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing both strontium and barium contamination. For the first time, by using correlated ⁸⁸Sr/⁸⁶Sr and ¹³⁸Ba/¹³⁶Ba ratios in mainstream SiC grains, we are able to resolve the effect of ¹³C concentration from that of ¹³C-pocket mass on s-process nucleosynthesis, which points toward the existence of large ¹³C pockets with low ¹³C concentrations in asymptotic giant branch stars. The presence of such large ¹³C pockets with a variety of relatively low ¹³C concentrations seems to require multiple mixing processes in parent asymptotic giant branch stars of mainstream SiC grains.

We develop a method to estimate photometric metallicities by simultaneously fitting the dereddened colors $u-g$, $g-r$, $r-i$, and $i-z$ from the SDSS with those predicted by the metallicity-dependent stellar loci. The method is tested with a spectroscopic sample of main-sequence stars in Stripe 82 selected from the SDSS DR9 and three open clusters. With 1% photometry, the method is capable of delivering photometric metallicities precise to about 0.05, 0.12, and 0.18 dex at metallicities of 0.0, −1.0, and −2.0, respectively, comparable to the precision achievable with low-resolution spectroscopy at a signal-to-noise ratio of 10. We apply this method to the re-calibrated Stripe 82 catalog and derive metallicities for about 0.5 million stars of colors $0.3\lt g-i\lt 1.6$ mag and distances between 0.3 and 18 kpc. Potential systematics in the metallicities thus derived, due to the contamination of giants and binaries, are investigated. Photometric distances are also calculated. About 91%, 72%, and 53% of the sample stars are brighter than r = 20.5, 19.5, and 18.5 mag, respectively. The median metallicity errors are around 0.19, 0.16, 0.11, and 0.085 dex for the whole sample, and for stars brighter than r = 20.5, 19.5, and 18.5 mag, respectively. The median distance errors are 8.8%, 8.4%, 7.7%, and 7.3% for the aforementioned four groups of stars, respectively. The data are publicly available. Potential applications of the data in studies of the distribution, (sub) structure, and chemistry of the Galactic stellar populations, are briefly discussed. The results will be presented in future papers.

We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new K-band Multi-Object Spectrograph Very Large Telescope, Chile. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = −0.52 ± 0.21, which agrees well with previous abundance studies of young stars and H ii regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physical properties determined for RSGs in NGC 6822 with those derived using the same technique in the Galaxy and the Magellanic Clouds, we show that there appears to be no significant temperature variation of RSGs with respect to metallicity, in contrast to recent evolutionary models.

The well-studied blazar 3C 279 underwent a giant γ-ray outburst in 2014 March–April. The measured γ-ray flux (1.21 ± 0.10 × 10⁻⁵$\;{\rm ph}\;{\rm c}{{{\rm m}}^{-2}}\;{{{\rm s}}^{-1}}$ in a 0.1–300 GeV energy range) is the highest detected from 3C 279 by the Fermi Large Area Telescope. Hour-scale γ-ray flux variability is observed, with a flux doubling time as short as 1.19 ± 0.36 hr detected during one flare. The γ-ray spectrum is found to be curved at the peak of the flare, suggesting low probability of detecting very high energy (VHE; E$\gt$ 100 GeV) emission, which is further confirmed by the VERITAS observations. The γ-ray flux increased by more than an order in comparison to a low-activity state and the flare consists of multiple sub-structures having a fast rise and slow decay profile. The flux enhancement is seen in all the wavebands, though at a lesser extent compared to γ-rays. During the flare, a considerable amount of the kinetic jet power gets converted to γ-rays and the jet becomes radiatively efficient. A one-zone leptonic emission model is used to reproduce the flare and we find increase in the bulk Lorentz factor as a major cause of the outburst. From the observed fast variability, lack of VHE detection, and the curved γ-ray spectrum, we conclude that the location of the emission region cannot be far out from the broad-line region (BLR) and contributions from both BLR and torus photons are required to explain the observed γ-ray spectrum.

We present a high spatial resolution (≈20 pc) of ¹²CO(2 −1) observations of the lenticular galaxy NGC 4526. We identify 103 resolved giant molecular clouds (GMCs) and measure their properties: size R, velocity dispersion σ_v, and luminosity L. This is the first GMC catalog of an early-type galaxy. We find that the GMC population in NGC 4526 is gravitationally bound, with a virial parameter α ∼ 1. The mass distribution, dN/dM ∝ M^{−2.39 ± 0.03}, is steeper than that for GMCs in the inner Milky Way, but comparable to that found in some late-type galaxies. We find no size–line width correlation for the NGC 4526 clouds, in contradiction to the expectation from Larson's relation. In general, the GMCs in NGC 4526 are more luminous, denser, and have a higher velocity dispersion than equal-size GMCs in the Milky Way and other galaxies in the Local Group. These may be due to higher interstellar radiation field than in the Milky Way disk and weaker external pressure than in the Galactic center. In addition, a kinematic measurement of cloud rotation shows that the rotation is driven by the galactic shear. For the vast majority of the clouds, the rotational energy is less than the turbulent and gravitational energy, while the four innermost clouds are unbound and will likely be torn apart by the strong shear at the galactic center. We combine our data with the archival data of other galaxies to show that the surface density Σ of GMCs is not approximately constant, as previously believed, but varies by ∼3 orders of magnitude. We also show that the size and velocity dispersion of the GMC population across galaxies are related to the surface density, as expected from the gravitational and pressure equilibrium, i.e., σ_vR^−1/2 ∝ Σ^1/2.

Radial velocity measurements, BVR_C photometry, and high-resolution spectroscopy in the wavelength region from blue to near-infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD 112869 with a unique ratio of carbon isotopes in the atmosphere. An LTE abundance analysis was carried out using the method of spectral synthesis and new self-consistent 1D atmospheric models. The radial velocity monitoring confirmed semiregular variations with a peak-to-peak amplitude of about 10 km ${{{\rm s}}^{-1}}$ and a dominating period of about 115 days. The light, color, and radial velocity variations are typical of the evolved pulsating stars. The atmosphere of HD 112869 appears to be less metal-poor than reported before, [Fe/H] = −2.3 ± 0.2 dex. Carbon-to-oxygen and carbon isotope ratios are found to be extremely high, C/O $\simeq$ 12.6 and¹²C/¹³C ≳ 1500, respectively. The s-process elements yttrium and barium are not enhanced, but neodymium appears to be overabundant. The magnesium abundance seems to be lower than the average found for CEMP stars, [Mg/Fe] < +0.4 dex. HD 112869 could be a single low-mass halo star in the stage of asymptotic giant branch evolution.

We present a study of the effects of high energy cosmic rays (CRs) over the astrophysical ices, observed toward the embedded class I protostar Elias 29, by using computational modeling and laboratory data. Its spectrum was observed with the Infrared Space Observatory (ISO) covering 2.3–190 μm. The modeling employed the three-dimensional Monte Carlo radiative transfer code RADMC-3D and laboratory data of bombarded ice grains by CR analogs and unprocessed ices (not bombarded). We are assuming that Elias 29 has a self-irradiated disk with inclination i = 600, surrounded by an envelope with a bipolar cavity. The results show that absorption features toward Elias 29 are better reproduced by assuming a combination between unprocessed astrophysical ices at low temperature (H₂O, CO, CO₂) and bombarded ices (H₂O:CO₂) by high energy CRs. Evidences of the ice processing around Elias 29 can be observed by the good fitting around 5.5–8.0 μm, by polar and apolar ice segregation in 15.15–15.25 μm, and by the presence of the CH₄ and HCOOH ices. Given that non-nitrogen compounds were employed in this work, we assume that absorption around 5.5–8.0 μm should not be associated with the NH₄⁺ ion (see the 2003 work of Shutte & Khanna ), but more probably with aliphatic ethers (e.g., R1-OCH₂-R2), CH₃CHO, and related species. The results obtained in this paper are important because they show that the environment around protostars is better modeled considering processed samples and, consequently, demonstrate the chemical evolution of the astrophysical ices.

Recent work by Levitan et al. has expanded the long-term photometric database for AM CVn stars. In particular, their outburst properties are well correlated with orbital period and allow constraints to be placed on the secular mass transfer rate between secondary and primary if one adopts the disk instability model for the outbursts. We use the observed range of outbursting behavior for AM CVn systems as a function of orbital period to place a constraint on mass transfer rate versus orbital period. We infer a rate ∼$5\times {{10}^{-9}}{{M}_{\odot }}\;{\rm y}{{{\rm r}}^{-1}}{{({{P}_{{\rm orb}}}/1000\;{\rm s})}^{-5.2}}$. We show that the functional form so obtained is consistent with the recurrence time–orbital period relation found by Levitan et al. using a simple theory for the recurrence time. Also, we predict that their steep dependence of outburst duration on orbital period will flatten considerably once the longer orbital period systems have more complete observations.

Ultraviolet (UV) and optical photometry of Type Ia supernovae (SNe Ia) at low redshift have revealed the existence of two distinct color groups, composed of NUV-red and NUV-blue events. The color curves differ primarily by an offset, with the NUV-blue $u-v$ color curves bluer than the NUV-red curves by 0.4 mag. For a sample of 23 low-redshift SNe Ia observed with Swift, the NUV-red group dominates by a ratio of 2:1. We compare rest-frame UV/optical spectrophotometry of intermediate- and high-redshift SNe Ia with UVOT photometry and Hubble Space Telescope spectrophotometry of low-redshift SNe Ia, finding that the same two color groups exist at higher redshift, but with the NUV-blue events as the dominant group. Within each red/blue group, we do not detect any offset in color for different redshifts, providing insight into how SN Ia UV emission evolves with redshift. Through spectral comparisons of SNe Ia with similar peak width and phase, we explore the wavelength range that produces the UV/optical color differences. We show that the ejecta velocity of NUV-red supernovae (SNe) is larger than that of NUV-blue objects by roughly 12% on average. This velocity difference can explain some of the UV/optical color difference, but differences in the strengths of spectral features seen in mean spectra require additional explanation. Because of the slightly different $b-v$ colors for these groups, NUV-red SNe will have their extinction underestimated using common techniques. This, in turn, leads to underestimation of the optical luminosity of the NUV-blue SNe Ia, in particular, for the high-redshift cosmological sample. Not accounting for this effect should thus produce a distance bias that increases with redshift and could significantly bias measurements of cosmological parameters.

We present a framework for forecasting cosmological constraints from future neutral hydrogen intensity mapping experiments at low to intermediate redshifts. In the process, we establish a simple way of comparing such surveys with optical galaxy redshift surveys. We explore a wide range of experimental configurations and assess how well a number of cosmological observables (the expansion rate, growth rate, and angular diameter distance) and parameters (the densities of dark energy and dark matter, spatial curvature, the dark energy equation of state, etc.) will be measured by an extensive roster of upcoming experiments. A number of potential contaminants and systematic effects are also studied in detail. The overall picture is encouraging—if autocorrelation calibration can be controlled to a sufficient level, Phase I of the Square Kilometre Array should be able to constrain the dark energy equation of state about as well as a DETF Stage IV galaxy redshift survey like Euclid, in roughly the same time frame.

Molecular outflows driven by protostellar cluster members likely impact their surroundings and contribute to turbulence, affecting subsequent star formation. The very young Serpens South cluster consists of a particularly high density and fraction of protostars, yielding a relevant case study for protostellar outflows and their impact on the cluster environment. We combined CO $J=1-0$ observations of this region using the Combined Array for Research in Millimeter-wave Astronomy and the Institut de Radioastronomie Millimétrique 30 m single-dish telescope. The combined map allows us to probe CO outflows within the central, most active region at size scales of 0.01–0.8 pc. We account for effects of line opacity and excitation temperature variations by incorporating ¹²CO and ¹³CO data for the J = 1 − 0 and J = 3 − 2 transitions (using Atacama Pathfinder Experiment and Caltech Submillimeter Observatory observations for the higher CO transitions), and we calculate mass, momentum, and energy of the molecular outflows in this region. The outflow mass-loss rate, force, and luminosity, compared with diagnostics of turbulence and gravity, suggest that outflows drive a sufficient amount of energy to sustain turbulence, but not enough energy to substantially counter the gravitational potential energy and disrupt the clump. Further, we compare Serpens South with the slightly more evolved cluster NGC 1333, and we propose an empirical scenario for outflow-cluster interaction at different evolutionary stages.

We present observations and initial analysis from a Hubble Space Telescope (HST) Cycle 19 program using STIS to obtain the first co-spatial, UV–optical spectra of 10 Galactic planetary nebulae (PNs). Our primary objective was to measure the critical emission lines of carbon and nitrogen with unprecedented signal-to-noise ratio (S/N) and spatial resolution over the wavelength range 1150–10270 Å, with the ultimate goal of quantifying the production of these elements in low- and intermediate-mass stars. Our sample was selected from PNs with a near-solar metallicity, but spanning a broad range in N/O based on published ground-based and IUE spectra. This study, the first of a series, concentrates on the observations and emission-line measurements obtained by integrating along the entire spatial extent of the slit. We derived ionic and total elemental abundances for the seven PNs with the strongest UV line detections (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC 5315, NGC 5882, and NGC 7662). We compare these new results with other recent studies of the nebulae and discuss the relative merits of deriving the total elemental abundances of C, N, and O using ionization correction factors (ICFs) versus summed abundances. For the seven PNs with the best UV line detections, we conclude that summed abundances from direct diagnostics of ions with measurable UV lines give the most accurate values for the total elemental abundances of C and N (although ICF abundances often produced good results for C). In some cases where significant discrepancies exist between our abundances and those from other studies, we show that the differences can often be attributed to their use of fluxes that are not co-spatial. Finally, we examined C/O and N/O versus O/H and He/H in well-observed Galactic, LMC, and SMC PNs and found that highly accurate abundances are essential for properly inferring elemental yields from their progenitor stars. Future papers will discuss photoionization modeling of our observations, of both the integrated spectra and spatial variations of the UV versus optical lines along the STIS slit lengths, which are unique to our observations.

The stellar kinematics of galactic disks are key to constraining disk formation and evolution processes. In this paper, for the first time, we measure the stellar age–velocity dispersion correlation in the inner 20 kpc (∼3.5 disk scale lengths) of M31 and show that it is dramatically different from that in the Milky Way (MW). We use optical Hubble Space Telescope/Advanced Camera for Surveys photometry of 5800 individual stars from the Panchromatic Hubble Andromeda Treasury survey and Keck/DEIMOS radial velocity measurements of the same stars from the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo survey. We show that the average line-of-sight dispersion is a steadily increasing function of age exterior to R = 10 kpc, increasing from $30\;{\rm km}\;{{{\rm s}}^{-1}}$ for the main-sequence stars to 90 km s⁻¹ for the red giant branch stars. This monotonic increase implies that a continuous or recurring process contributed to the evolution of the disk. Both the slope and normalization of the dispersion versus age relation are significantly larger than in the MW, allowing for the possibility that the disk of M31 has had a more violent history than the disk of the MW, more in line with Λ cold dark matter predictions. We also find evidence for an inhomogeneous distribution of stars from a second kinematical component in addition to the dominant disk component. One of the largest and hottest high-dispersion patches is present in all age bins and may be the signature of the end of the long bar.

We present the first self-consistent simulations of the coupled spin-shape evolution of small gravitational aggregates under the influence of the YORP effect. Because of YORP's sensitivity to surface topography, even small centrifugally driven reconfigurations of aggregates can alter the YORP torque dramatically, resulting in spin evolution that can differ qualitatively from the rigid-body prediction. One-third of our simulations follow a simple evolution described as a modified YORP cycle. Two-thirds exhibit one or more of three distinct behaviors—stochastic YORP, self-governed YORP, and stagnating YORP—which together result in YORP self-limitation. Self-limitation confines rotation rates of evolving aggregates to far narrower ranges than those expected in the classical YORP cycle, greatly prolonging the times over which objects can preserve their sense of rotation. Simulated objects are initially randomly packed, disordered aggregates of identical spheres in rotating equilibrium, with low internal angles of friction. Their shape evolution is characterized by rearrangement of the entire body, including the deep interior. They do not evolve to axisymmetric top shapes with equatorial ridges. Mass loss occurs in one-third of the simulations, typically in small amounts from the ends of a prolate-triaxial body. We conjecture that YORP self-limitation may inhibit formation of top-shapes, binaries, or both, by restricting the amount of angular momentum that can be imparted to a deformable body. Stochastic YORP, in particular, will affect the evolution of collisional families whose orbits drift apart under the influence of Yarkovsky forces, in observable ways.

Galaxies with stellar masses near M* contain the majority of stellar mass in the universe, and are therefore of special interest in the study of galaxy evolution. The Milky Way (MW) and Andromeda (M31) have present-day stellar masses near M*, at 5 × 10¹⁰ M_☉ (defined here to be MW-mass) and 10¹¹ M_☉ (defined to be M31-mass). We study the typical progenitors of these galaxies using the FourStar Galaxy Evolution Survey (ZFOURGE). ZFOURGE is a deep medium-band near-IR imaging survey, which is sensitive to the progenitors of these galaxies out to z ∼ 3. We use abundance-matching techniques to identify the main progenitors of these galaxies at higher redshifts. We measure the evolution in the stellar mass, rest-frame colors, morphologies, far-IR luminosities, and star formation rates, combining our deep multiwavelength imaging with near-IR Hubble Space Telescope imaging from Cosmic Near-IR Deep Extragalactic Legacy Survey (CANDELS), and Spitzer and Herschel far-IR imaging from Great Observatories Origins Deep Survey-Herschel and CANDELS-Herschel. The typical MW-mass and M31-mass progenitors passed through the same evolution stages, evolving from blue, star-forming disk galaxies at the earliest stages to redder dust-obscured IR-luminous galaxies in intermediate stages and to red, more quiescent galaxies at their latest stages. The progenitors of the MW-mass galaxies reached each evolutionary stage at later times (lower redshifts) and with stellar masses that are a factor of two to three lower than the progenitors of the M31-mass galaxies. The process driving this evolution, including the suppression of star formation in present-day M* galaxies, requires an evolving stellar-mass/halo-mass ratio and/or evolving halo-mass threshold for quiescent galaxies. The effective size and SFRs imply that the baryonic cold-gas fractions drop as galaxies evolve from high redshift to z ∼ 0 and are strongly anticorrelated with an increase in the Sérsic index. Therefore, the growth of galaxy bulges in M* galaxies corresponds to a rapid decline in the galaxy gas fractions and/or a decrease in the star formation efficiency.

Ground level enhancements (GLEs) are relativistic solar particles measured at ground level by the worldwide network of cosmic ray detectors. These sporadic events are associated with solar flares and are assumed to be of a quasi-random nature. Studying them gives information about their source and propagation processes, the maximum capacity of the Sun as a particle accelerator engine, the magnetic structure of the medium traversed, etc. Space vehicles, as well as electric transformers and gas pipes at high latitudes may be damaged by this kind of radiation. As a result, their prediction has turned out to be very important, but because of their random occurrence, up to now few efforts toward this goal have been made. The results of these efforts have been limited to possible warnings in real time, just before a GLE occurrence, but no specific dates have been predicted well enough in advance to prevent possible hazards. In this study we show that, in spite of the quasi-stochastic nature of GLEs, it is possible to predict them with relative precision, even for future solar cycles. Additionally, a previous study establishing synchronization among some periodicities of several layers of solar atmosphere argues against the full randomness of the phenomenon of relativistic particle production. Therefore, by means of wavelet spectral analysis combined with fuzzy logic tools, we reproduce previous known GLE events and present results for future events. The next GLE is expected to occur in the first semester of 2016.

We present zoom-in N-body + hydrodynamic simulations of dwarf central galaxies formed in warm dark matter (WDM) halos with present-day masses of 2–4 × ${{10}^{10}}$M_⊙. Two different cases are considered: the first one when halo masses are close to the corresponding half-mode filtering scale, M_f (${{m}_{{\rm WDM}}}$ = 1.2 keV), and the second when they are 20 to 30 times the corresponding M_f (${{m}_{{\rm WDM}}}$ = 3.0 keV). The WDM simulations are compared with the respective cold dark matter (CDM) simulations. The dwarfs formed in halos of masses (20–30)M_f have roughly similar properties and evolution to their CDM counterparts; on the contrary, those formed in halos of masses around M_f, are systematically different from their CDM counterparts. As compared to the CDM dwarfs, they assemble the dark and stellar masses later, having mass-weighted stellar ages 1.4–4.8 Gyr younger; their circular velocity profiles are shallower, with maximal velocities 20%–60% lower; their stellar distributions are much less centrally concentrated and with larger effective radii, by factors of 1.3–3. The WDM dwarfs at the filtering scale (${{m}_{{\rm WDM}}}$ = 1.2 keV) have disk-like structures, and end in most cases with higher gas fractions and lower stellar-to-total mass ratios than their CDM counterparts. The late halo assembly, low halo concentrations, and the absence of satellites of the former with respect to the latter are at the basis of the differences.

We present kinematical analyses of 22 Galactic globular clusters using the Hubble Space Telescope proper motion catalogs recently presented in Bellini et al. For most clusters, this is the first proper-motion study ever performed, and, for many, this is the most detailed kinematic study of any kind. We use cleaned samples of bright stars to determine binned velocity-dispersion and velocity-anisotropy radial profiles and two-dimensional velocity-dispersion spatial maps. Using these profiles, we search for correlations between cluster kinematics and structural properties. We find the following: (1) more centrally concentrated clusters have steeper radial velocity-dispersion profiles; (2) on average, at 1σ confidence in two dimensions, the photometric and kinematic centers of globular clusters agree to within ∼1'', with a cluster-to-cluster rms of 4''(including observational uncertainties); (3) on average, the cores of globular clusters have isotropic velocity distributions to within 1% (${{\sigma }_{t}}/{{\sigma }_{r}}=0.992\pm 0.005$), with a cluster-to-cluster rms of 2% (including observational uncertainties); (4) clusters generally have mildly radially anisotropic velocity distributions (${{\sigma }_{t}}/{{\sigma }_{r}}\approx 0.8$–1.0) near the half-mass–radius, with bigger deviations from isotropy for clusters with longer relaxation times; and (5) there is a relation between ${{\sigma }_{{\rm minor}}}/{{\sigma }_{{\rm major}}}$ and ellipticity, such that the more flattened clusters in the sample tend to be more anisotropic, with ${{\sigma }_{{\rm minor}}}/{{\sigma }_{{\rm major}}}\approx 0.9$–1.0. Aside from these general results and correlations, the profiles and maps presented here can provide a basis for detailed dynamical modeling of individual globular clusters. Given the quality of the data, this is likely to provide new insights into a range of topics concerning globular cluster mass profiles, structure, and dynamics.

We explore the degree of magnetization at the jet base of M87 by using the observational data of the event horizon telescope (EHT) at 230 GHz obtained by Doeleman et al. By utilizing the method in Kino et al., we derive the energy densities of the magnetic fields (U_B) and electrons and positrons (${{U}_{\pm }}$) in the compact region detected by EHT (the EHT region) with its FWHM size $40\;\mu {\rm as}$. First, we assume that an optically thick region for synchrotron self-absorption (SSA) exists in the EHT region. Then, we find that the SSA-thick region should not be too large, in order to not overproduce the Poynting power at the EHT region. The allowed ranges of the angular size and the magnetic-field strength of the SSA-thick region are $21\;\mu {\rm as}\leqslant {{\theta }_{{\rm thick}}}\leqslant 26.3\;\mu {\rm as}$ and $50\;{\rm G}\leqslant {{B}_{{\rm tot}}}\leqslant 124\;{\rm G}$, respectively. Correspondingly, ${{U}_{B}}\gg {{U}_{\pm }}$ is realized in this case. We further examine the composition of plasma and energy density of protons by utilizing the Faraday rotation measurement at 230 GHz obtained by Kuo et al. Then, we find that ${{U}_{B}}\gg {{U}_{\pm }}+{{U}_{p}}$ still holds in the SSA-thick region. Second, we examine the case when the EHT region is fully SSA-thin. Then, we find that ${{U}_{B}}\gg {{U}_{\pm }}$ still holds unless protons are relativistic. Thus, we conclude that the magnetically driven jet scenario in M87 is viable in terms of energetics close to the Innermost Stable Circular Orbit scale unless the EHT region is fully SSA-thin and relativistic protons dominated.

We present an analysis of the orbital motion of the four substellar objects orbiting HR 8799. Our study relies on the published astrometric history of this system augmented with an epoch obtained with the Project 1640 coronagraph with an integral field spectrograph (IFS) installed at the Palomar Hale telescope. We first focus on the intricacies associated with astrometric estimation using the combination of an extreme adaptive optics system (PALM-3000), a coronagraph, and an IFS. We introduce two new algorithms. The first one retrieves the stellar focal plane position when the star is occulted by a coronagraphic stop. The second one yields precise astrometric and spectrophotometric estimates of faint point sources even when they are initially buried in the speckle noise. The second part of our paper is devoted to studying orbital motion in this system. In order to complement the orbital architectures discussed in the literature, we determine an ensemble of likely Keplerian orbits for HR 8799bcde, using a Bayesian analysis with maximally vague priors regarding the overall configuration of the system. Although the astrometric history is currently too scarce to formally rule out coplanarity, HR 8799d appears to be misaligned with respect to the most likely planes of HR 8799bce orbits. This misalignment is sufficient to question the strictly coplanar assumption made by various authors when identifying a Laplace resonance as a potential architecture. Finally, we establish a high likelihood that HR 8799de have dynamical masses below $13 M_{{\rm Jup}}$, using a loose dynamical survival argument based on geometric close encounters. We illustrate how future dynamical analyses will further constrain dynamical masses in the entire system.

The primordial internal structures of gas giant planets are unknown. Often giant planets are modeled under the assumption that they are adiabatic, convective, and homogeneously mixed, but this is not necessarily correct. In this work, we present the first self-consistent calculation of convective transport of both heat and material as the planets evolve. We examine how planetary evolution depends on the initial composition and its distribution, whether the internal structure changes with time, and if so, how it affects the evolution. We consider various primordial distributions, different compositions, and different mixing efficiencies and follow the distribution of heavy elements in a Jupiter-mass planet as it evolves. We show that a heavy-element core cannot be eroded by convection if there is a sharp compositional change at the core-envelope boundary. If the heavy elements are initially distributed within the planet according to some compositional gradient, mixing occurs in the outer regions resulting in a compositionally homogeneous outer envelope. Mixing of heavy materials that are injected in a convective gaseous envelope are found to mix efficiently. Our work demonstrates that the primordial internal structure of a giant planet plays a substantial role in determining its long-term evolution and that giant planets can have non-adiabatic interiors. These results emphasize the importance of coupling formation, evolution, and internal structure models of giant planets self-consistently.

An intriguing trend among Kepler's multi-planet systems is an overabundance of planet pairs with period ratios just wide of a mean motion resonance (MMR) and a dearth of systems just narrow of them. Traditional planet formation models are at odds with these observations. They are also in contrast with the period ratios of radial-velocity-discovered multi-planet systems which tend to pile up at $2:1$ MMR. We propose that gas–disk migration traps planets in an MMR. After gas dispersal, orbits of these trapped planets are altered through interaction with a residual planetesimal disk. We study the effects of planetesimal disk interactions on planet pairs trapped in $2:1$ MMR using planets of mass typical of the Kepler planet candidates and explore large ranges for the mass, and density profile of the planetesimal disk. We find that planet–planetesimal disk interactions naturally create the observed asymmetry in period-ratio distribution for large ranges of planetesimal disk and planet properties. If the planetesimal disk mass is above a threshold of ≈0.2× the planet mass, these interactions typically disrupt MMR. Afterwards, the planets migrate in such a way that the final period-ratio is slightly higher than the integer ratio corresponding to the initial MMR. Below this threshold these interactions typically cannot disrupt the resonance and the period ratio stays close to the integer ratio. The threshold explains why the more massive planet pairs found by RV surveys are still in resonance. We encourage future research to explore how significantly the associated accretion would change the planets' atmospheric and surface properties.

The remarkable Hubble Space Telescope (HST) data sets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map the evolution of the rest-frame UV luminosity function (LF) from $z\sim 10$ to $z\sim 4$. We develop new color criteria that more optimally utilize the full wavelength coverage from the optical, near-IR, and mid-IR observations over our search fields, while simultaneously minimizing the incompleteness and eliminating redshift gaps. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at $z\sim 4$, $z\sim 5$, $z\sim 6$, $z\sim 7$, $z\sim 8$, and $z\sim 10$, respectively, from the ∼1000 arcmin² area covered by these data sets. This sample of >10,000 galaxy candidates at $z\geqslant 4$ is by far the largest assembled to date with HST. The selection of $z\,\sim$ 4–8 candidates over the five CANDELS fields allows us to assess the cosmic variance; the largest variations are at $z\geqslant 7$. Our new LF determinations at $z\sim 4$ and $z\sim 5$ span a 6 mag baseline and reach to –16 AB mag. These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of $\gt {{L}^{*}}$ galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to $3.4\sigma$ significance for a steeper faint-end slope of the UV LF at $z\gt 4$, with α evolving from $\alpha =-1.64\pm 0.04$ at $z\sim 4$ to $\alpha =-2.06\pm 0.13$ at $z\sim 7$ (and $\alpha =-2.02\pm 0.23$ at $z\sim 8$), consistent with that expected from the evolution of the halo mass function. We find less evolution in the characteristic magnitude M^* from $z\sim 7$ to $z\sim 4;$ the observed evolution in the LF is now largely represented by changes in ${{\phi }^{*}}$. No evidence for a non-Schechter-like form to the z ∼ 4–8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio $(\propto {{(1+z)}^{-1.5}})$ of halos provides a good representation of the observed evolution.

We present a backward approach for the interpretation of the evolution of the near-IR and the far-IR luminosity functions (LFs) across the redshift range $0\lt z\lt 3$. In our method, late-type galaxies are treated by means of a parametric phenomenological method based on PEP/HerMES data up to z ∼ 4, whereas spheroids are described by means of a physically motivated backward model. The spectral evolution of spheroids is modeled by means of a single-mass model, associated with a present-day elliptical with a K-band luminosity comparable to the break of the local early-type LF. The formation of proto-spheroids is assumed to occurr across the redshift range $1\leqslant z\leqslant 5$. The key parameter is represented by the redshift ${{z}_{0.5}}$ at which half of all proto-spheroids are already formed. For this parameter, a statistical study indicates values between ${{z}_{0.5}}=1.5$ and ${{z}_{0.5}}=3$. We assume ${{z}_{0.5}}\sim 2$ as the fiducial value and show that this assumption allows us to describe accourately the redshift distributions and the source counts. By assuming ${{z}_{0.5}}\sim 2$ at the far-IR flux limit of the PEP-COSMOS survey, the PEP-selected sources observed at $z\gt 2$ can be explained as progenitors of local spheroids caught during their formation. We also test the effects of mass downsizing by dividing the spheroids into three populations of different present-day stellar masses. The results obtained in this case confirm the validity of our approach, i.e., that the bulk of proto-spheroids can be modeled by means of a single model that describes the evolution of galaxies at the break of the present-day early-type K-band LF.

Observational consequences of tidal disruption of stars by supermassive black holes (SMBHs) can enable us to discover quiescent SMBHs, constrain their mass function, and study  the formation and evolution of transient accretion disks and jet formation. A couple of jetted tidal disruption events (TDEs) have been recently claimed in hard X-rays, challenging jet models,  which were previously applied to γ-ray bursts and active galactic nuclei. It is therefore of paramount importance to increase the current sample. In this paper, we find that the best strategy is not to use upcoming X-ray instruments alone, which will yield between several (eRosita) and a couple of hundred (Einstein Probe) events per year below redshift one. We rather claim that a more efficient TDE hunter will be the Square Kilometer Array (SKA) operating in survey mode at 1.4 GHz. It may detect up to several hundred events per year below z ∼ 2.5 with a peak rate of a few tens per year at z ≈ 0.5. Therefore, even if the jet production efficiency is not 100% as assumed here, the predicted rates should be large enough to allow for statistical studies. The characteristic TDE decay of ${{t}^{-5/3}}$, however, is not seen in radio, whose flux emission is quite featureless. Identification therefore requires localization and prompt repointing by higher energy instruments. If radio candidates would be repointed within a day by future X-ray observatories (e.g., Athena- and LOFT-like missions), it will be possible to detect up to ≈400 X-ray counterparts, almost up to redshift 2. The shortcoming is that only for redshift below ≈0.4 will the trigger times be less than 10 days from the explosion. In this regard the X-ray surveys are better suited to probe the beginning of the flare, and are therefore complementary to SKA.

We report on the effects of cosmic rays (CRs) on the abundance of CO in H₂ clouds under conditions typical for star-forming galaxies in the universe. We discover that this most important molecule for tracing H₂ gas is very effectively destroyed in ISM environments with CR energy densities ${{U}_{{\rm CR}}}\sim (50-{{10}^{3}})\times {{U}_{{\rm CR},{\rm Gal}}}$, a range expected in numerous star-forming systems throughout the universe. This density-dependent effect operates volumetrically rather than only on molecular cloud surfaces (i.e., unlike FUV radiation that also destroys CO), and is facilitated by (a) the direct destruction of CO by CRs and (b) a reaction channel activated by CR-produced He⁺. The effect we uncover is strong enough to render Milky-Way-type Giant Molecular Clouds very CO-poor (and thus CO-untraceable), even in ISM environments with rather modestly enhanced average CR energy densities of ${{U}_{{\rm CR}}}\sim (10-50)\times {{{\rm U}}_{{\rm CR},{\rm Gal}}}$. We conclude that the CR-induced destruction of CO in molecular clouds, unhindered by dust absorption, is perhaps the single most important factor controlling the CO-visibility of molecular gas in vigorously star-forming galaxies. We anticipate that a second-order effect of this CO destruction mechanism will be to make the H₂ distribution in the gas-rich disks of such galaxies appear much clumpier in CO J = 1–0, 2–1 line emission than it actually is. Finally we give an analytical approximation of the CO/H₂ abundance ratio as a function of gas density and CR energy density for use in galaxy-size or cosmological hydrodynamical simulations, and propose some key observational tests.

I present high-resolution column density maps of two molecular clouds (MCs) having strikingly different star formation rates. To better understand the unusual, massive G216-2.5, an MC with no massive star formation, the distribution of its molecular gas is compared to that of the Rosette MC. Far-infrared data from Herschel are used to derive N(H₂) maps of each cloud and are combined with ${{I}_{{\rm CO}}}$ data to determine the CO-to-H₂ ratio, ${{X}_{{\rm CO}}}$. In addition, the probability distribution functions (PDFs) and cumulative mass fractions of the clouds are compared. For G216-2.5, $\langle N({{{\rm H}}_{2}})\rangle =7.8\times {{10}^{20}}$ cm⁻² and $\langle {{X}_{{\rm CO}}}\rangle =2.2\times {{10}^{20}}$ cm⁻² (K km s⁻¹)⁻¹; for the Rosette, $\langle N({{{\rm H}}_{2}})\rangle =1.8\times {{10}^{21}}$ cm⁻² and $\langle {{X}_{{\rm CO}}}\rangle =2.8\times {{10}^{20}}$ cm⁻² (K km s⁻¹)⁻¹. The PDFs of both clouds are log-normal for extinctions below ∼2 mag and both show departures from log-normality at high extinctions. Although it is the less-massive cloud, the Rosette has a higher fraction of its mass in the form of dense gas and contains $1389\;{{M}_{\odot }}$ of gas above the so-called extinction threshold for star formation, ${{A}_{V}}=7.3$ mag. The G216-2.5 cloud has $874\;{{M}_{\odot }}$ of dense gas above this threshold.

We report on the Submillimeter Array (SMA) observations of molecular lines at 270 GHz toward the W3(OH) and W3(H₂O) complex. Although previous observations already resolved the W3(H₂O) into two or three sub-components, the physical and chemical properties of the two sources are not well constrained. Our SMA observations clearly resolved the W3(OH) and W3(H₂O) continuum cores. Taking advantage of the line fitting tool XCLASS, we identified and modeled a rich molecular spectrum in this complex, including multiple CH₃CN and CH₃OH transitions in both cores. HDO, C₂H₅CN, O¹³CS, and vibrationally excited lines of HCN, CH₃CN, and CH₃OCHO were only detected in W3(H₂O). We calculate gas temperatures and column densities for both cores. The results show that W3(H₂O) has higher gas temperatures and larger column densities than W3(OH) as previously observed, suggesting physical and chemical differences between the two cores. We compare the molecular abundances in W3(H₂O) to those in the Sgr B2(N) hot core, the Orion KL hot core, and the Orion Compact Ridge, and discuss the chemical origin of specific species. An east–west velocity gradient is seen in W3(H₂O), and the extension is consistent with the bipolar outflow orientation traced by water masers and radio jets. A north–south velocity gradient across W3(OH) is also observed. However, with current observations we cannot be assured whether the velocity gradients are caused by rotation, outflow, or radial velocity differences of the sub-components of W3(OH).

We present new Hubble Space Telescope (HST) multi-epoch ultraviolet (UV) spectra of the bright Type IIb SN 2013df, and undertake a comprehensive analysis of the set of four SNe IIb for which HST UV spectra are available (SN 1993J, SN 2001ig, SN 2011dh, and SN 2013df). We find strong diversity in both continuum levels and line features among these objects. We use radiative-transfer models that fit the optical part of the spectrum well, and find that in three of these four events we see a UV continuum flux excess, apparently unaffected by line absorption. We hypothesize that this emission originates above the photosphere, and is related to interaction with circumstellar material (CSM) located in close proximity to the SN progenitor. In contrast, the spectra of SN 2001ig are well fit by single-temperature models, display weak continuum and strong reverse-fluorescence features, and are similar to spectra of radioactive ⁵⁶Ni-dominated SNe Ia. A comparison of the early shock-cooling components in the observed light curves with the UV continuum levels which we assume trace the strength of CSM interaction suggests that events with slower cooling have stronger CSM emission. The radio emission from events having a prominent UV excess is perhaps consistent with slower blast-wave velocities, as expected if the explosion shock was slowed down by the CSM that is also responsible for the strong UV, but this connection is currently speculative as it is based on only a few events.

This paper examines flows in the immediate vicinity of stars and compact objects dynamically inspiralling within a common envelope (CE). Flow in the vicinity of the embedded object is gravitationally focused, leading to drag and potentially to gas accretion. This process has been studied numerically and analytically in the context of Hoyle–Lyttleton accretion (HLA). Yet, within a CE, accretion structures may span a large fraction of the envelope radius, and in so doing sweep across a substantial radial gradient of density. We quantify these gradients using detailed stellar evolution models for a range of CE encounters. We provide estimates of typical scales in CE encounters that involve main sequence stars, white dwarfs, neutron stars, and black holes with giant-branch companions of a wide range of masses. We apply these typical scales to hydrodynamic simulations of three-dimensional HLA with an upstream density gradient. This density gradient breaks the symmetry that defines HLA flow, and imposes an angular momentum barrier to accretion. Material that is focused into the vicinity of the embedded object thus may not be able to accrete. As a result, accretion rates drop dramatically, by one to two orders of magnitude, while drag rates are only mildly affected. We provide fitting formulae to the numerically derived rates of drag and accretion as a function of the density gradient. The reduced ratio of accretion to drag suggests that objects that can efficiently gain mass during CE evolution, such as black holes and neutron stars, may grow less than implied by the HLA formalism.

We investigate small-scale dynamo action in the solar convection zone through a series of high-resolution MHD simulations in a local Cartesian domain with $1\;{{R}_{\odot }}$ (solar radius) of horizontal extent and a radial extent from 0.715 to $0.96\;{{R}_{\odot }}$. The dependence of the solution on resolution and diffusivity is studied. For a grid spacing of less than 350 km, the rms magnetic field strength near the base of the convection zone reaches 95% of the equipartition field strength (i.e., magnetic and kinetic energy are comparable). For these solutions the Lorentz force feedback on the convection velocity is found to be significant. The velocity near the base of the convection zone is reduced to 50% of the hydrodynamic one. In spite of the significant decrease of the convection velocity, the reduction in the enthalpy flux is relatively small, since the magnetic field also suppresses the horizontal mixing of the entropy between up- and downflow regions. This effect increases the amplitude of the entropy perturbation and makes convective energy transport more efficient. We discuss potential implications of these results for solar global convection and dynamo simulations.

Magnetohydrodynamic (MHD) kink waves are ubiquitously observed in the solar atmosphere. The propagation and damping of these waves may play relevant roles in the transport and dissipation of energy in the solar atmospheric medium. However, in the atmospheric plasma dissipation of transverse MHD wave energy by viscosity or resistivity needs very small spatial scales to be efficient. Here, we theoretically investigate the generation of small scales in nonuniform solar magnetic flux tubes due to phase mixing of MHD kink waves. We go beyond the usual approach based on the existence of a global quasi-mode that is damped in time due to resonant absorption. Instead, we use a modal expansion to express the MHD kink wave as a superposition of Alfvén continuum modes that are phase mixed as time evolves. The comparison of the two techniques evidences that the modal analysis is more physically transparent and describes both the damping of global kink motions and the building up of small scales due to phase mixing. In addition, we discuss that the processes of resonant absorption and phase mixing are closely linked. They represent two aspects of the same underlying physical mechanism: the energy cascade from large scales to small scales due to naturally occurring plasma and/or magnetic field inhomogeneities. This process may provide the necessary scenario for efficient dissipation of transverse MHD wave energy in the solar atmospheric plasma.

The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet Sun. These bright grains are seen with the IRIS 1330, 1400, and 2796 Å slit-jaw filters. We combine coordinated observations with IRIS and from the ground with the Swedish 1 m Solar Telescope (SST) which allows us to have chromospheric (Ca ii 8542 Å, Ca ii H 3968 Å, Hα, and Mg ii k 2796 Å) and transition region (C ii 1334 Å, Si iv 1403 Å) spectral imaging, and single-wavelength Stokes maps in Fe i 6302 Å at high spatial ($0\buildrel{\prime\prime}\over{.} 33$), temporal, and spectral resolution. We conclude that the IRIS slit-jaw grains are the counterpart of so-called acoustic grains, i.e., resulting from chromospheric acoustic waves in a non-magnetic environment. We compare slit-jaw images (SJIs) with spectra from the IRIS spectrograph. We conclude that the grain intensity in the 2796 Å slit-jaw filter comes from both the Mg ii k core and wings. The signal in the C ii and Si iv lines is too weak to explain the presence of grains in the 1300 and 1400 Å SJIs and we conclude that the grain signal in these passbands comes mostly from the continuum. Although weak, the characteristic shock signatures of acoustic grains can often be detected in IRIS C ii spectra. For some grains, a spectral signature can be found in IRIS Si iv. This suggests that upward propagating acoustic waves sometimes reach all the way up to the transition region.

The shapes of cosmic voids are prone to distortions caused by external tidal forces since their low densities imply a lower internal resistance. This susceptibility of the void shapes to tidal distortions makes them useful as indicators of large-scale tidal and density fields, despite the practical difficulty in defining them. Using the void catalog constructed by Pan et al. from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7), we detect a clear $4\sigma$ signal of spatial correlations of the void shapes on a scale of $20\;{{h}^{-1}}$ Mpc and show that the signal is robust against the projection of the void shapes onto the plane of sky. By constructing a simple analytic model for the void shape correlation, within the framework of tidal torque theory, we demonstrate that the void shape correlation function scales linearly with the two-point correlation function of the linear density field. We also find direct observational evidence for the cross-correlation of the void shapes with the large-scale velocity shear field that was linearly reconstructed by Lee et al. from SDSS DR7. We discuss the possibility of using the void shape correlation function to break the degeneracy between the density parameter and the power spectrum amplitude and to independently constrain the neutrino mass as well.

Cosmic shear can only be measured where there are galaxies. This source-lens clustering (SLC) effect has two sources, intrinsic source clustering and cosmic magnification (magnification/size bias). Lensing tomography can suppress the former. However, this reduction is limited by the existence of photo-z error and nonzero redshift bin width. Furthermore, SLC induced by cosmic magnification cannot be reduced by lensing tomography. Through N-body simulations, we quantify the impact of SLC on the lensing power spectrum in the context of lensing tomography. We consider both the standard estimator and the pixel-based estimator. We find that none of them can satisfactorily handle both sources of SLC. (1) For the standard estimator, SLC induced by both sources can bias the lensing power spectrum by $\mathcal{O}\left( 1 \right)$–$\mathcal{O}(10)\%$. Intrinsic source clustering also increases statistical uncertainties in the measured lensing power spectrum. However, the standard estimator suppresses intrinsic source clustering in the cross-spectrum. (2) In contrast, the pixel-based estimator suppresses SLC through cosmic magnification. However, it fails to suppress SLC through intrinsic source clustering and the measured lensing power spectrum can be biased low by $\mathcal{O}\left( 1 \right)$–$\mathcal{O}(10)\%$. In short, for typical photo-z errors (${{\sigma }_{z}}/\left( 1+z \right)=0.05$) and photo-z bin sizes (${\Delta}{{z}^{P}}=0.2$), SLC alters the lensing E-mode power spectrum by 1–10%, with $\ell \sim {{10}^{3}}$ and ${{z}_{s}}\sim 1$ being of particular interest to weak lensing cosmology. Therefore the SLC is a severe systematic for cosmology in Stage-IV lensing surveys. We present useful scaling relations to self-calibrate the SLC effect.

In the preceding paper, we showed that large second-order anisotropies of heliospheric ions measured by the Voyager 1 space probe during the August 2012 boundary crossing event could be explained by a magnetic shear across the heliopause preventing particles streaming along the magnetic field from escaping the inner heliosheath. According to Stone et al., the penetration distance of heliospheric ions into the outer heliosheath had a strong dependence on the particle's Larmor radius. By comparing hydrogen, helium, and oxygen ions with the same energy per nucleon, these authors argued that this effect must be attributed to larger cyclotron radii of heavier species rather than differences in velocity. We propose that gradient drift in a nonuniform magnetic field was the cause of both the large second-order anisotropies and the spatial differentiation based on the ion's rigidity. A latitudinal gradient of magnetic field strength of about 10% per AU between 2012.7 and 2012.9 could have provided drift motion sufficient to match both LECP and CRS Voyager 1 observations. We explain the transient intensity dropout observed prior to the heliocliff using flux tube structures embedded in the heliosheath and magnetically connected to interstellar space. Finally, this paper reports a new indirect measurement of the plasma radial velocity at the heliopause on the basis of the time difference between two cosmic-ray telescopes measuring the same intensity dropout.

X-ray observations of galaxy clusters have detected numerous X-ray cavities, evolved from the interaction of active galactic nucleus (AGN) jets with the intracluster medium (ICM) and providing compelling evidence for the importance of jet-mode AGN feedback. Here we argue for the physical importance of the cavity shape, which we characterize with two geometric parameters: radial elongation τ and top wideness b. We study the cavity shape with 16 hydrodynamic jet simulations in two representative clusters, and find that the shapes of young cavities are mainly determined by various jet properties. Our simulations successfully reproduce two observed types of young cavities elongated along either the jet ($\tau \gt 1$; type-II) or the perpendicular ($\tau \leqslant 1$; type-I) direction. Bottom-wide type-I cavities are produced by very light internally subsonic jets, while top-wide type-II cavities are produced by heavier, internally supersonic jets, which may also produce center-wide cavities with $\tau \sim 1$ if the jets are only slightly supersonic. Bottom-wide type-II cavities can be produced by very light jets with very long durations and cylindrical cavities are produced by very light internally supersonic jets. While not appreciably affecting the shapes of young cavities, viscosity significantly affects the long-term cavity evolution, suppressing both interface instabilities and the formation of torus-like morphology. We encourage observers to study the shapes of young and old X-ray cavities separately, the former probing the properties of AGN jets and the latter potentially probing the ICM viscosity level.