Table of contents

A database can be accessed on the Web at http://edd.ifa.hawaii.edu that was developed to promote access to information related to galaxy distances. The database has three functional components. First, tables from many literature sources have been gathered and enhanced with links through a distinct galaxy naming convention. Second, comparisons of results both at the levels of parameters and of techniques have begun and are continuing, leading to increasing homogeneity and consistency of distance measurements. Third, new material is presented arising from ongoing observational programs at the University of Hawaii 2.2 m telescope, radio telescopes at Green Bank, Arecibo, and Parkes and with the Hubble Space Telescope. This new observational material is made available in tandem with related material drawn from archives and passed through common analysis pipelines.

The color–magnitude diagrams/tip of the red giant branch (CMDs/TRGB) section of the Extragalactic Distance Database contains a compilation of observations of nearby galaxies from the Hubble Space Telescope. Approximately 250 (and increasing) galaxies in the Local Volume have CMDs and the stellar photometry tables used to produce them available through the Web. Various stellar populations that make up a galaxy are visible in the CMDs, but our primary purpose for collecting and analyzing these galaxy images is to measure the TRGB in each. We can estimate the distance to a galaxy by using stars at the TRGB as standard candles. In this paper, we describe the process of constructing the CMDs and make the results available to the public.

We present the catalog of H i sources extracted from the ongoing Arecibo Legacy Fast ALFA (ALFALFA) extragalactic H i line survey, found within the sky region bounded by 9^h36^m < α < 11^h36^m and +08° < δ < +12°. The H i catalog presented here for this 118 deg² region is combined with the ones derived from surrounding regions also covered by the ALFALFA survey to examine the large-scale structure in the complex Leo region. Because of the combination of wide sky coverage and superior sensitivity, spatial and spectral resolution, the ALFALFA H i catalog of the Leo region improves significantly on the numbers of low H i mass sources as compared with those found in previous H i surveys. The H i mass function of the Leo I group presented here is dominated by low-mass objects: 45 of the 65 Leo I members have $M_{\rm H\,{\scriptscriptstyle I}} < 10^{8} M_{\odot }$, yielding tight constraints on the low-mass slope of the Leo I H i mass function. The best-fit slope is α ≃ −1.41 + 0.2 − 0.1. A direct comparison between the ALFALFA H i line detections and an optical search of the Leo I region proves the advantage of the ALFALFA strategy in finding low-mass, gas-rich dwarfs. These results suggest the existence of a significant population of low surface brightness, gas-rich, yet still very low H i mass galaxies, and may reflect the same type of morphological segregation as is seen in the Local Group. While the low-mass end slope of the Leo I H i mass function is steeper than that determined for luminosity functions of the group, the slope still falls short of the values predicted by simulations of structure formation in the lambda cold dark matter paradigm.

The rest-frame far-ultraviolet morphologies of eight nearby interacting and starburst galaxies (Arp 269, M 82, Mrk 8, NGC 520, NGC 1068, NGC 3079, NGC 3310, and NGC 7673) are compared with 54 galaxies at z ∼  1.5 and 46 galaxies at z ∼  4 observed in the Great Observatories Origins Deep Survey (GOODS) taken with the Advanced Camera for Surveys onboard the Hubble Space Telescope. The nearby sample is artificially redshifted to z ∼  1.5 and 4 by applying luminosity and size scaling. We compare the simulated galaxy morphologies to real z ∼  1.5 and 4 UV-bright galaxy morphologies. We calculate the Gini coefficient (G), the second-order moment of the brightest 20% of the galaxy's flux (M₂₀), and the Sérsic index (n). We explore the use of nonparametric methods with two-dimensional profile fitting and find the combination of M₂₀ with n an efficient method to classify galaxies as having merger, exponential disk, or bulge-like morphologies. When classified according to G and M₂₀ 20/30% of real/simulated galaxies at z ∼  1.5 and 37/12% at z ∼  4 have bulge-like morphologies. The rest have merger-like or intermediate distributions. Alternatively, when classified according to the Sérsic index, 70% of the z ∼  1.5 and z ∼  4 real galaxies are exponential disks or bulge-like with n>0.8, and ∼ 30% of the real galaxies are classified as mergers. The artificially redshifted galaxies have n values with ∼ 35% bulge or exponential at z ∼  1.5 and 4. Therefore, ∼ 20%–30% of Lyman-break galaxies have structures similar to local starburst mergers, and may be driven by similar processes. We assume merger-like or clumpy star-forming galaxies in the GOODS field have morphological structure with values n < 0.8 and M₂₀> − 1.7. We conclude that Mrk 8, NGC 3079, and NGC 7673 have structures similar to those of merger-like and clumpy star-forming galaxies observed at z ∼  1.5 and 4.

We present ultraviolet, optical, and near-infrared photometry as well as optical spectra of the peculiar supernova (SN) 2008ha. SN 2008ha had a very low peak luminosity, reaching only M_V = −14.2 mag, and low line velocities of only ∼2000 km s⁻¹ near maximum brightness, indicating a very small kinetic energy per unit mass of ejecta. Spectroscopically, SN 2008ha is a member of the SN 2002cx-like class of SNe, a peculiar subclass of SNe Ia; however, SN 2008ha is the most extreme member, being significantly fainter and having lower line velocities than the typical member, which is already ∼2 mag fainter and has line velocities ∼5000 km s⁻¹ smaller (near maximum brightness) than a normal SN Ia. SN 2008ha had a remarkably short rise time of only ∼10 days, significantly shorter than either SN 2002cx-like objects (∼15 days) or normal SNe Ia (∼19.5 days). The bolometric light curve of SN 2008ha indicates that SN 2008ha peaked at L_peak = (9.5 ± 1.4) × 10⁴⁰ erg s⁻¹, making SN 2008ha perhaps the least luminous SN ever observed. From its peak luminosity and rise time, we infer that SN 2008ha generated (3.0 ± 0.9) × 10⁻³M_☉ of ⁵⁶Ni, had a kinetic energy of ∼2 × 10⁴⁸ erg, and ejected 0.15 M_☉ of material. The host galaxy of SN 2008ha has a luminosity, star formation rate, and metallicity similar to those of the Large magellanic Cloud. We classify three new (and one potential) members of the SN 2002cx-like class, expanding the sample to 14 (and one potential) members. The host-galaxy morphology distribution of the class is consistent with that of SNe Ia, Ib, Ic, and II. Several models for generating low-luminosity SNe can explain the observations of SN 2008ha; however, if a single model is to describe all SN 2002cx-like objects, deflagration of carbon–oxygen white dwarfs, with SN 2008ha being a partial deflagration and not unbinding the progenitor star, is preferred. The rate of SN 2008ha-like events is ∼10% of the SN Ia rate, and in the upcoming era of transient surveys, several thousand similar objects may be discovered, suggesting that SN 2008ha may be the tip of a low-luminosity transient iceberg.

We calibrate the baryonic Tully–Fisher (BTF) relation using a sample of gas-dominated galaxies. These determine the absolute scale of the baryonic mass–rotation speed relation independent of the choice of stellar mass estimator. We find a BTF slope of 3.94 ± 0.07 (random) ±0.08 (systematic) and a zero point of 1.79 ± 0.26 (random) ±0.25 (systematic). We apply this relation to estimate the stellar masses of star-dominated galaxies. This procedure reproduces the trend of mass-to-light ratio with color predicted by population synthesis models. The normalization is also correct, consistent with empirical estimates of the initial mass function used in such models.

The discovery of new Wolf–Rayet (WR) stars in our Galaxy via large-scale narrowband optical surveys has been severely limited by dust extinction. Recent improvements in infrared technology have made narrowband–broadband imaging surveys viable again. We report a new J, K, and narrowband imaging survey of 300 deg² of the plane of the Galaxy, spanning 150 degrees in Galactic longitude and reaching 1 degree above and below the Galactic plane. The survey has a useful limiting magnitude of K = 15 over most of the observed Galactic plane, and K = 14 within a few degrees of the Galactic center. Thousands of emission line candidates have been detected. In spectrographic follow-ups of 173 WR star candidates we have discovered 41 new WR stars, 15 of type WN and 26 of type WC. Star subtype assignments have been confirmed with K-band spectra, and distances approximated using the method of spectroscopic parallax. A few of the new WR stars are among the most distant known in our Galaxy. The distribution of these new WR stars is seen to follow that of previously known WR stars along the spiral arms of the Galaxy. Tentative radial velocities were also measured for most of the new WR stars.

We examine the nature of brightness fluctuations in the UV–Optical spectral region of an ordinary quasar with 894 optical brightness measurements made during the epoch 1993–1999. We find evidence for systematic trends having the character of a pattern of reverberations following an initial disturbance. The initial pulses have brightness increases of the order of 20% and pulse widths of 50 days, and the reverberations have typical amplitudes of 12% with longer mean pulse widths of the order of 80 days and pulse separations of an order of 90 days. The repeat pattern occurs over the same timescales whether the initial disturbance is a brightening or fading. The lags of the pulse trains are comparable to the lags seen previously in reverberation of the broad blueshifted emission lines following brightness disturbances in Seyfert galaxies, when allowance is made for the mass of the central object. In addition to the burst pulse trains, we find evidence for a semiperiodicity with a timescale of two years. These strong patterns of brightness fluctuations suggest a method of discovering quasars from photometric monitoring alone, with data of the quality expected from large brightness monitoring programs such as Pan-STARRS and LSST.

Kuiper Belt dwarf planet 136472 Makemake, formerly known as 2005 FY9, is currently the third-largest known object in the Kuiper Belt, after the dwarf planets Pluto and Eris. It is currently second only to Pluto in apparent brightness, due to Eris' much larger heliocentric distance. Makemake shows very little photometric variability, which has prevented confident determination of its rotation period until now. Using extremely precise time-series photometry, we find that the rotation period of Makemake is 7.7710 ±  0.0030 hr, where the uncertainty is a 90% confidence interval. An alias period is detected at 11.41 hr, but is determined with approximately 95% confidence not to be the true period. Makemake's 7.77 hr rotation period is in the typical range for Kuiper Belt objects, consistent with Makemake's apparent lack of a substantial satellite to alter its rotation through tides. The amplitude of Makemake's photometric light curve is 0.0286 ±  0.0016 mag in V. This amplitude is about 10 times less than Pluto's, which is surprising given the two objects' similar sizes and spectral characteristics. Makemake's photometric variability is instead similar to that of Eris, which is so small that no confident rotation period has yet been determined. It has been suggested that dwarf planets such as Makemake and Eris, both farther from the Sun and colder than Pluto, exhibit lower photometric variability because they are covered with a uniform layer of frost. Such a frost is probably the correct explanation for Eris. However, it may be inconsistent with the spectrum of Makemake, which resembles reddish Pluto more than neutrally colored Eris. Makemake may instead be a more Pluto-like object that we observe at present with a nearly pole-on viewing geometry—a possibility that can be tested with continuing observations over the coming decades.

High-resolution (∼1 arcmin) astronomical imaging at low frequency (⩽150 MHz) has only recently become practical with the development of new calibration algorithms for removing ionospheric distortions. In addition to opening a new window in observational astronomy, the process of calibrating the ionospheric distortions also probes ionospheric structure in an unprecedented way. Here we explore one aspect of this new type of ionospheric measurement: the differential refraction of celestial source pairs as a function of their angular separation. This measurement probes variations in the spatial gradient of the line-of-sight total electron content (TEC) to ∼10⁻³ TECU km⁻¹ (1 TECU = 10¹² cm⁻²) accuracy over spatial scales of under 10 km to over 100 km. We use data from the VLA Low-frequency Sky Survey (VLSS), a nearly complete 74 MHz survey of the entire sky visible to the VLA telescope in Socorro, New Mexico. These data comprise over 500 hr of observations, all calibrated in a standard way. While ionospheric spatial structure varies greatly from one observation to the next, when analyzed over hundreds of hours, statistical patterns become apparent. We present a detailed characterization of how the median differential refraction depends on source pair separation, elevation, and time of day. We find that elevation effects are large, but geometrically predictable and can be "removed" analytically using a "thin-shell" model of the ionosphere. We find significantly greater ionospheric spatial variations during the day than at night. These diurnal variations appear to affect the larger angular scales to a greater degree indicating that they come from disturbances on relatively larger spatial scales (hundreds of kilometers, rather than tens of kilometers).

In 1970–1971, V1057 Cyg rose from about m_pg ≈ 16 to a peak near 10.5 mag. It has subsequently faded to about B = 15, and although it appeared to be a T Tauri star (TTS) before the outburst, it now resembles a rather peculiar rapidly rotating G-type supergiant. Before the outburst, it showed unmistakable evidence of high-velocity outflow (by the suppression of emission Ca ii λ3968 by the P Cyg absorption component of H λ3970). Such outflow absorptions are currently found at many strong lines (Hα, Na i D_1,2, K i λλ7664, 7698, Ca ii λλ8498, 8662,  ...). The same phenomenon has since been observed in a number of other FUors near maximum light, suggesting that it is a FUor characteristic that clearly differs from the outflows found in TTSs. The Li i resonance line at 6707 Å is relatively weak, and on high-resolution spectra obtained between 1997 and 2008 showed variable absorption structure on its shortward side that probably represents wind structure that is lost in the stronger lines. In addition, a narrow emission line at 6707 Å persists throughout the series and is the counterpart of the sharp emission lines that occur near the centers of many of the broad stellar absorption lines (v sin i = 55 km s⁻¹) and that were responsible for the line-splitting phenomenon formerly regarded as evidence of a Keplerian disk. Given the evidence of a quasi-permanent outflow at V1057 Cyg, the hypothesis is advanced that a FUor outburst may be the result of a rapidly rotating TTS having contracted to a point of rotational instability, at which time it sheds enough material and angular momentum to resume contraction, until the next such event.

We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with the InfraRed Array Camera and the Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the H i spatial distribution. We observe a probable detection at 8 μm and a marginal detection at 24 μm associated with the highest H i column densities in the cloud. At 70 and 160 μm, upper limits on the dust emission are deduced. The level of the detection is low so that the possibility of a fortuitous cirrus clump or of an overdensity of extragalactic sources along the line of sight cannot be excluded. If this detection is confirmed, the quantities of dust inferred imply a dust-to-gas ratio in the intergalactic cloud up to a few times solar but no less than 1/20 solar. A confirmed detection would therefore exclude the possibility that the intergalactic cloud has a primordial origin. Instead, this large intergalactic cloud could therefore have been formed through interactions between galaxies in the group.

We present distance determinations for two Local Group dwarf spheroidal galaxies, Carina and Fornax, based on the near-infrared magnitudes of the tip of the red giant branch (TRGB). For Carina we derive true distance moduli of 20.09 and 20.13 mag in the J and K bands, respectively, while for Fornax the same distance modulus of 20.84 mag was derived in both filters. The statistical errors of these determinations are of the order of 0.03–0.04 mag, whereas the systematic uncertainties on the distances are 0.12 mag in the J band and 0.14 mag in the K band. The distances obtained from the near-infrared TRGB method in this paper agree very well with those obtained for these two galaxies from optical calibrations of the TRGB method, their horizontal branches, RR Lyrae variables, and the near-infrared magnitudes of their red clumps.

We have identified 4659 variable objects in the Northern Sky Variability Survey. We have classified each of these objects into one of the five variable star classes: (1) Algol/β Lyr systems including semidetached, and detached eclipsing binaries, (2) W Ursae Majoris overcontact and ellipsoidal variables, (3) long-period variables such as Cepheid and Mira-type objects, (4) RR Lyr pulsating variables, and (5) short-period variables including δ Scuti stars. All the candidates have outside of eclipse magnitudes of ∼10–13. The primary classification tool is the use of Fourier coefficients combined with period information and light-curve properties to make the initial classification. Brief manual inspection was done on all light curves to remove nonperiodic variables that happened to slip through the process and to quantify any errors in the classification pipeline. We list the coordinates, period, Two Micron All Sky Survey colors, total amplitude variation, and any previous classification of the object. 548 objects previously identified as Algols in our previous paper are not included here.

New CCD photometric observations of the eclipsing system AR Boo were obtained from 2006 February to 2008 April. The star's photometric properties are derived from detailed studies of the period variability and of all available light curves. We find that over about 56 yr the orbital period of the system has varied due to a combination of an upward parabola and a sinusoid rather than in a monotonic fashion. Mass transfer from the less massive primary to the more massive secondary component is likely responsible for at least a significant part of the secular period change. The cyclical variation with a period of 7.57 yr and a semi-amplitude of 0.0015 d can be produced either by a light-travel-time effect due to an unseen companion with a scaled mass of M₃sin i₃ = 0.081 M_☉ or by a magnetic period modulation in the secondary star. Historical light curves of AR Boo, as well as our own, display season-to-season light variability, which are best modeled by including both a cool spot and a hot one on the secondary star. We think that the spots express magnetic dynamo-related activity and offer limited support for preferring the magnetic interpretation of the 7.57 yr cycle over the third-body interpretation. Our solutions confirm that AR Boo belongs to the W-subtype contact binary class, consisting of a hotter, less massive primary star with a spectral type of G9 and a companion of spectral type K1.

Gemini North adaptive optics (AO) imaging spectroscopy is presented for the Galactic ultracompact H ii (UCH ii) region K3 − 50A. Data were obtained in the K band using the Near-infrared Integral Field Spectrograph (NIFS) behind the facility AO module ALTAIR in natural guide star mode. The NIFS data cube reveals a complex spatial morphology across the 0.1 pc scale of the 3'' UCH ii region. Comparison of the nebular emission to Cloudy ionization models shows that the central source must have an effective temperature between about 37,000 K and 45,000 K with preferred values near 40,000 K. Evidence is presented for sharp density variations in the nebula which are interpreted as a clearing of material nearest the central source. High excitation lines of Fe iii and Se iv show that the ionization of the nebula clearly changes with distance from the central source. A double lobed kinematic signature (± 25 km s⁻¹) is evident in the Brγ line map which may be related to the larger scale ionized flow detailed in earlier investigations. This signature and the large-scale flow are not co-aligned, but they may still be related. Though clearly resolved from the nebula, the central source itself remains buried, and the NIFS spectrum shows no evidence of photospheric lines.

Fossil groups are systems with one single central elliptical galaxy and an unusual lack of luminous galaxies in the inner regions. The standard explanation for the formation of these systems suggests that the lack of bright galaxies is due to galactic cannibalism. In this study, we show the results of an optical and X-ray analysis of RX J1340.6+4018, the prototype fossil group. The data indicate that RX J1340.6+4018 is similar to clusters in almost every sense (dynamical mass, X-ray luminosity, M/L, and luminosity function) except for the lack of L* galaxies. There are claims in the literature that fossil systems have a lack of small mass halos, compared to predictions based on the lambda cold dark matter scenario. The observational data gathered on this and other fossil groups so far offer no support for this idea. Analysis of the SN Ia/SN II ejecta ratio in the inner and outer regions shows a marginally significant central dominance of SN Ia material. This suggests that either the merger which originated in the central galaxy was dry or the group has been formed at early epochs, although better data are needed to confirm this result.

We present a spectroscopic study of the N159/N160 massive star-forming region south of 30 Doradus in the Large Magellanic Cloud, classifying a total of 189 stars in the field of the complex. Most of them belong to O and early B spectral classes; we have also found some uncommon and very interesting spectra, including members of the Onfp class, a Be P Cygni star, and some possible multiple systems. Using spectral types as broad indicators of evolutionary stages, we considered the evolutionary status of the region as a whole. We infer that massive stars at different evolutionary stages are present throughout the region, favoring the idea of a common time for the origin of recent star formation in the N159/N160 complex as a whole, while sequential star formation at different rates is probably present in several subregions.

We have obtained near-infrared spectra covering the Ca II triplet lines for a large number of stars associated with 16 Small Magellanic Cloud (SMC) clusters using the VLT + FORS2. These data compose the largest available sample of SMC clusters with spectroscopically derived abundances and velocities. Our clusters span a wide range of ages and provide good areal coverage of the galaxy. Cluster members are selected using a combination of their positions relative to the cluster center as well as their location in the color–magnitude diagram, abundances, and radial velocities (RVs). We determine mean cluster velocities to typically 2.7 km s⁻¹ and metallicities to 0.05 dex (random errors), from an average of 6.4 members per cluster. By combining our clusters with previously published results, we compile a sample of 25 clusters on a homogeneous metallicity scale and with relatively small metallicity errors, and thereby investigate the metallicity distribution, metallicity gradient, and age–metallicity relation (AMR) of the SMC cluster system. For all 25 clusters in our expanded sample, the mean metallicity [Fe/H] = −0.96 with σ = 0.19. The metallicity distribution may possibly be bimodal, with peaks at ∼−0.9 dex and −1.15 dex. Similar to the Large Magellanic Cloud (LMC), the SMC cluster system gives no indication of a radial metallicity gradient. However, intermediate age SMC clusters are both significantly more metal-poor and have a larger metallicity spread than their LMC counterparts. Our AMR shows evidence for three phases: a very early (>11 Gyr) phase in which the metallicity reached ∼−1.2 dex, a long intermediate phase from ∼10 to 3 Gyr in which the metallicity only slightly increased, and a final phase from 3 to 1 Gyr ago in which the rate of enrichment was substantially faster. We find good overall agreement with the model of Pagel & Tautvaišiene, which assumes a burst of star formation at 4 Gyr. Finally, we find that the mean RV of the cluster system is 148 km s⁻¹, with a velocity dispersion of 23.6 km s⁻¹ and no obvious signs of rotation amongst the clusters. Our result is similar to what has been found from a wide variety of kinematic tracers in the SMC, and shows that the SMC is best represented as a pressure supported system.

We develop an automated spectral synthesis technique for the estimation of metallicities ([Fe/H]) and carbon abundances ([C/Fe]) for metal-poor stars, including carbon-enhanced metal-poor stars, for which other methods may prove insufficient. This technique, autoMOOG, is designed to operate on relatively strong features visible in even low- to medium-resolution spectra, yielding results comparable to much more telescope-intensive high-resolution studies. We validate this method by comparison with 913 stars which have existing high-resolution and low- to medium-resolution to medium-resolution spectra, and that cover a wide range of stellar parameters. We find that at low metallicities ([Fe/H] ≲−2.0), we successfully recover both the metallicity and carbon abundance, where possible, with an accuracy of ∼0.20 dex. At higher metallicities, due to issues of continuum placement in spectral normalization done prior to the running of autoMOOG, a general underestimate of the overall metallicity of a star is seen, although the carbon abundance is still successfully recovered. As a result, this method is only recommended for use on samples of stars of known sufficiently low metallicity. For these low-metallicity stars, however, autoMOOG performs much more consistently and quickly than similar, existing techniques, which should allow for analyses of large samples of metal-poor stars in the near future. Steps to improve and correct the continuum placement difficulties are being pursued.

CCD photometric observations of the visual binary, V345 Geminorum, obtained from 2007 January 24 to 2009 March 22, are presented. When comparing the light curves in 2007 and 2008, it is found that there appears to be an O'Connell effect in the light curves of 2008. From those observations, two sets of photometric solutions were deduced using the 2003 version of the W–D program. The results indicated that V345 Gem is a low mass ratio overcontact binary with f = 72.9%(±3.1%). The asymmetric light curves in 2008 may be attributed to the activity of starspot, whose area is up to 1.55% of the area of the more massive component. The contributions of the third light to the total light are approximately 20% in the BVR bands. The absolute physical parameters for V345 Gem were obtained first. From the log L–log M diagram of the binary-star evolution, the primary component is an evolved star. From the O−C curve for V345 Gem, it is discovered that there exists a long-term period increase with a cyclic variation. The period and amplitude of the cyclic variation are P₃ = 646.7(±0.7) day and A = 00019(±00002), which may be caused by the light-time effect via the assumed third body. If it is true, the visual binary V345 Gem may be a quadruple star. The kind of additional component may remove angular momentum from the central system, which may play an important role for the formation and evolution of the binary. The secular period increases at a rate of dP/dt = +5.88 × 10⁻⁸ d yr^-1, indicating that the mass transfers from the less massive component to the more massive component. With mass transferring, the orbital angular momentum decreases while the spin angular momentum increases. When J_spin/J_orb > 1/3, this kind of deep, low mass ratio overcontact binary with secular period increase may evolve into a rapid-rotating single star.

We have obtained velocity dispersions from Keck high-resolution integrated spectroscopy of 10 M31 globular clusters (GCs), including three candidate intermediate-age GCs. We show that these candidates have the same V-band mass-to-light (M/L_V) ratios as the other GCs, implying that they are likely to be old. We also find a trend of derived velocity dispersion with wavelength, but cannot distinguish between a systematic error and a physical effect. Our new measurements are combined with photometric and spectroscopic data from the literature in a re-analysis of all M31 GC M/L_V values. In a combined sample of 27 GCs, we show that the metal-rich GCs have lowerM/L_V than the metal-poor GCs, in conflict with predictions from stellar population models. Fragmentary data for other galaxies support this observation. The M31 GC fundamental plane is extremely tight, and we follow up an earlier suggestion by Djorgovski to show that the fundamental plane can be used to estimate accurate distances (potentially 10% or better).

IAC-pop is a code designed to solve the star formation history (SFH) of a complex stellar population system, like a galaxy, from the analysis of the color–magnitude diagram (CMD). It uses a genetic algorithm to minimize a χ² merit function comparing the star distributions in the observed CMD and the CMD of a synthetic stellar population. A parameterization of the CMDs is used, which is the main input of the code. In fact, the code can be applied to any problem in which a similar parameterization of an experimental set of data and models can be made. The method's internal consistency and robustness against several error sources, including observational effects, data sampling, and stellar evolution library differences, are tested. It is found that the best stability of the solution and the best way to estimate errors are obtained by several runs of IAC-pop with varying the input data parameterization. The routine MinnIAC is used to control this process. IAC-pop is offered for free use and can be downloaded from the site http://iac-star.iac.es/iac-pop. The routine MinnIAC is also offered under request, but support cannot be provided for its use. The only requirement for the use of IAC-pop and MinnIAC is referencing this paper and crediting as indicated in the site.

We conducted a search for occultations of bright stars by Kuiper Belt Objects (KBOs) to estimate the density of subkilometer KBOs in the sky. We report here the first results of this occultation survey of the outer solar system conducted in 2007 June and 2008 June/July at the MMT Observatory using Megacam, the large MMT optical imager. We used Megacam in a novel shutterless continuous-readout mode to achieve high-precision photometry at 200 Hz, which with point-spread function convolution results in an effective sampling of ∼30 Hz. We present an analysis of 220 star hours of data at a signal-to-noise ratio of 25 or greater, taken from images of fields within 3° of the ecliptic plane. The survey efficiency is greater than 10% for occultations by KBOs of diameter d ⩾ 0.7 km, and we report no detections in our data set. We set a new 95% confidence level upper limit for the surface density Σ_N(d) of KBOs larger than 1 km: Σ_N(d ⩾ 1 km) ⩽ 2.0 × 10⁸ deg⁻², and for KBOs larger than 0.7 km Σ_N(d ⩾ 0.7 km) ⩽ 4.8 × 10⁸ deg⁻².

We identify a population of morphologically defined E/S0 galaxies lying on the locus of late-type galaxies in color–stellar mass space—the "blue sequence"—at the present epoch. Using three samples (from the Nearby Field Galaxy Survey or NFGS, a merged HyperLeda/Sloan Digital Sky Survey/Two Micron All Sky Survey catalog, and the NYU Value-Added Galaxy Catalog), we analyze blue-sequence E/S0s with stellar masses ≳10⁸M_☉, arguing that individual objects may be evolving either up toward the red sequence or down into the blue sequence. Blue-sequence E/S0 galaxies become more common with decreasing stellar mass, comprising ≲2% of E/S0s near the "shutdown mass" M_s ∼ 1–2 × 10¹¹ M_☉, increasing to ≳5% near the "bimodality mass" M_b ∼ 3 × 10¹⁰ M_☉, and sharply rising to ≳ 20%–30% below the "threshold mass" M_t ∼ 4–6 × 10⁹ M_☉, down to our completeness analysis limit at ∼10⁹ M_☉. The strong emergence of blue-sequence E/S0s below M_t coincides with a previously reported global increase in mean atomic gas fractions below M_t for galaxies of all types on both sequences, suggesting that the availability of cold gas may be basic to blue-sequence E/S0s' existence. Environmental analysis reveals that many sub-M_b blue-sequence E/S0s reside in low-to-intermediate density environments. Thus, the bulk of the population we analyze appears distinct from the generally lower-mass cluster dE population; S0 morphologies with a range of bulge sizes are typical. In mass–radius and mass–σ scaling relations, blue-sequence E/S0s are more similar to red-sequence E/S0s than to late-type galaxies, but they represent a transitional class. While some of them, especially in the high-mass range from M_b to M_s, resemble major-merger remnants that will likely fade onto the red sequence, most blue-sequence E/S0s below M_b show signs of disk and/or pseudobulge building, which may be enhanced by companion interactions. The blue overall colors of blue-sequence E/S0s are most clearly linked to blue outer disks, but also reflect blue centers and more frequent blue-centered color gradients than seen in red-sequence E/S0s. Notably, all E/S0s in the NFGS with polar or counterrotating gas lie on or near the blue sequence, and most of these systems show signs of secondary stellar disks forming in the decoupled gas. From star formation rates and gas fractions, we infer significant recent and ongoing morphological transformation in the blue-sequence E/S0 population, especially below M_b. We argue that sub-M_b blue-sequence E/S0s occupy a "sweet spot" in stellar mass and concentration, with both abundant gas and optimally efficient star formation, which may enable the formation of large spiral disks. Our results provide evidence for the importance of disk rebuilding after mergers, as predicted by hierarchical models of galaxy formation.

The catalog from the first high-resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble's Wide-Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained far-ultraviolet (FUV, 1614 Å) data with Hubble's Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with GALEX. We detected 31 sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented.

The hot subdwarf (sd) stars in the Palomar Green (PG) catalog of ultraviolet excess (UVX) objects play a key role in investigations of the frequency and types of binary companions and the distribution of orbital periods. These are important for establishing whether and by which channels the sd stars arise from interactions in close binary systems. It has been suggested that the list of PG sd stars is biased by the exclusion of many stars in binaries, whose spectra show the Ca ii K line in absorption. A total of 1125 objects that were photometrically selected as candidates were ultimately rejected from the final PG catalog using this K–line criterion. We study 88 of these "PG-Rejects" (PGRs), to assess whether there are significant numbers of unrecognized sd stars in binaries among the PGR objects. The presence of an sd should cause a large UVX, compared with the cool K–line star. We assemble GALEX, Johnson V, and Two Micron All Sky Survey photometry and compare the colors of these PGR objects with those of known sd stars, cool single stars, and hot+cool binaries. Sixteen PGRs were detected in both the far-ultraviolet (FUV) and near-ultraviolet GALEX passbands. Eleven of these, plus the 72 cases with only an upper limit in the FUV band, are interpreted as single cool stars, appropriately rejected by the PG spectroscopy. Of the remaining five stars, three are consistent with being sd stars paired with a cool main-sequence companion, while two may be single stars or composite systems of another type. We discuss the implications of these findings for the 1125 PGR objects as a whole. An enlarged study is desirable to increase confidence in these first results and to identify individual sd+cool binaries or other composites for follow-up study. The GALEX All-sky Imaging Survey data have sufficient sensitivity to carry out this larger study.

Chromospheric model calculations of the Hα line for selected red giant branch and asymptotic giant branch (AGB) stars in the globular clusters M13, M15, and M92 are constructed to derive mass loss rates (MLRs). The model spectra are compared to the observations obtained with the Hectochelle on the MMT telescope. These stars show strong Hα emissions and blueshifted Hα cores signaling that mass outflow is present in all stars. Outflow velocities of 3–19 km s⁻¹, larger than indicated by Hα profiles, are needed in the upper chromosphere to achieve good agreement between the model spectra and the observations. The resulting MLRs range from 0.6 × 10⁻⁹ to 5 × 10⁻⁹ M_☉ yr⁻¹, which are about an order of magnitude lower than predicted from "Reimers' law" or inferred from the infrared excess of similar stars. The MLR increases slightly with luminosity and with decreasing effective temperature. Stars in the more metal-rich M13 have higher MLRs by a factor of ∼2 than in the metal-poor clusters M15 and M92. A fit to the MLRs is given by $\dot{M}$ (M_☉ yr⁻¹) = 0.092 ×L^0.16 × T^−2.02_eff × A^0.37, where $A=10^{[\rm Fe/H]}$. Multiple observations of stars revealed one object in M15, K757, in which the mass outflow increased by a factor of 6 between two observations separated by 18 months. Other stars showed changes in MLR by a factor of 1.5 or less.

Comet 17P/Holmes had a massive outburst at approximately 2007 October 23.8 and its total brightness reached maximum (from m = 17 to m = 2.5) around 2007 October 25, about 1.7 days (42 hr) after the event. Following the first report of this extraordinary cometary outburst, comprehensive observations were obtained at the Lulin Observatory until early 2008 January by using broadband filters and narrowband cometary filters. The separation velocity, as projected on the plane of the sky, between the nucleus and the coma blob produced by the outburst has been estimated to be 0.132 ± 0.004 km s^-1 from October 25.8 to November 1.6. The expansion speed, also projected on the plane of the sky of the dust shell has been found to be constant at a rate of approximately 0.554 ± 0.005 km s^-1 from October 25.8 to November 1.6. The color on December 10 is slightly redder than that of the Sun. Our narrowband observations provide information on the production rates of gas species on October 31: log Q (CN) = 27.103 and log Q (C₂) = 27.349. The resulting abundance ratios show that the comet 17P can be classified as a "typical comet" in terms of composition.

We present a flare rate analysis of 50,130 M dwarf light curves in Sloan Digital Sky Survey Stripe 82. We identified 271 flares using a customized variability index to search ∼2.5 million photometric observations for flux increases in the u and g bands. Every image of a flaring observation was examined by eye and with a point-spread function-matching and image subtraction tool to guard against false positives. Flaring is found to be strongly correlated with the appearance of Hα in emission in the quiet spectrum. Of the 99 flare stars that have spectra, we classify eight as relatively inactive. The flaring fraction is found to increase strongly in stars with redder colors during quiescence, which can be attributed to the increasing flare visibility and increasing active fraction for redder stars. The flaring fraction is strongly correlated with |Z| distance such that most stars that flare are within 300 pc of the Galactic plane. We derive flare u-band luminosities and find that the most luminous flares occur on the earlier-type m dwarfs. Our best estimate of the lower limit on the flaring rate (averaged over Stripe 82) for flares with Δu ⩾ 0.7 mag on stars with u < 22 is 1.3 flares hr⁻¹ deg⁻² but can vary significantly with the line of sight.

Exo-Dat is a database and an information system created primarily in support of the exoplanet program of the COnvection ROtation & planetary Transits (CoRoT) mission. In the directions of CoRoT pointings, it provides a united interface to several sets of data: stellar published catalogs, photometric and spectroscopic data obtained during the mission preparation, results from the mission and from follow-up observations, and several mission-specific technical parameters. The new photometric data constitute the subcatalog Exo-Cat, and give consistent 4-color photometry of 14.0 million stars with a completeness to 19th magnitude in the r-filter. It covers several zones in the galactic plane around CoRoT pointings, with a total area of 209 deg². This Exo-Dat information system provides essential technical support to the ongoing CoRoT light-curve analyses and ground-based follow-up by supplying additional complementary information such as the prior knowledge of the star's fundamental parameters or its contamination level inside the large CoRoT photometric mask. The database is fully interfaced with VO tools and thus benefits from existing visualization and analysis tools like TOPCAT or ALADIN. It is accessible to the CoRoT community through the Web, and will be gradually opened to the public. It is the ideal tool to prepare the foreseen statistical studies of the properties of the exoplanetary systems. As a VO-compliant system, such analyses could thus benefit from the most up-to-date classifier tools.

A new catalog of visual double systems containing eclipsing binaries as one component is presented. The main purpose of this catalog is to compile a complete list of all known multiples of this variety, both for current analysis and to highlight those in need of additional observations. All available photometric and astrometric data were analyzed, resulting in new orbits for eight systems and new times of minimum light for a number of the eclipsing binaries. Some of the systems in the catalog have acceptable solutions for their visual orbits, although in most cases their orbital periods are too long for simultaneous analysis. Also included, however, are a number of systems which currently lack an orbital solution but which may be suitable for simultaneous analysis in the future.

We present B-, V-, and I-band CCD photometry of the W UMa-type binary system TX Cnc, which is a member star of the Praesepe open cluster. Based on the observations, new ephemeris and a revised photometric solution of the binary system were derived. Combined with the results of the radial velocity solution contributed by Pribulla et al., the absolute parameters of the system were determined. The mass, radius, and luminosity of the primary component are derived to be 1.35 ± 0.02 M_☉, 1.27 ± 0.04 R_☉, and 2.13 ± 0.11 L_☉. Those for the secondary star are computed as 0.61 ± 0.01 M_☉, 0.89 ± 0.03 R_☉, and 1.26 ± 0.07 L_☉, respectively. Based on these results, a distance modulus of (m − M)_V = 6.34 ± 0.05 is determined for the star. It confirms the membership of TX Cnc to the Praesepe open cluster. The evolutionary status and the physical nature of the binary system are discussed compared with the theoretical model.

We report the discovery of oscillations in the hot subdwarf B (sdB) star JL 166 from time-series photometry using the Goodman Spectrograph on the 4.1 m Southern Astrophysical Research Telescope. Previous spectroscopic and photometric observations place the star near the hot end of the empirical sdB instability strip and imply the presence of a cool companion. Amplitude spectra of the stellar light curve reveal at least 10 independent pulsation modes with periods ranging from 97 to 178 s and amplitudes from 0.9 to 4 mma. We adopt atmospheric parameters of T_eff = 34,350 K and log g = 5.75 from a model atmosphere analysis of our time-averaged, medium-resolution spectrum.

Spitzer MIPS 24 μm images were obtained for 36 Galactic planetary nebulae (PNe) whose central stars are hot white dwarfs (WDs) or pre-WDs with effective temperatures of ∼100,000 K or higher. Diffuse 24 μm emission is detected in 28 of these PNe. The eight nondetections are angularly large PNe with very low Hα surface brightnesses. We find three types of correspondence between the 24 μm emission and Hα line emission of these PNe: six show 24 μm emission more extended than Hα emission, nine have a similar extent at 24 μm and Hα, and 13 show diffuse 24 μm emission near the center of the Hα shell. The sizes and surface brightnesses of these three groups of PNe and the nondetections suggest an evolutionary sequence, with the youngest ones being brightest and the most evolved ones undetected. The 24 μm band emission from these PNe is attributed to [O  iv] 25.9 μm and [Ne v] 24.3 μm line emission and dust continuum emission, but the relative contributions of these three components depend on the temperature of the central star and the distribution of gas and dust in the nebula.