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Photographic spectra of Plaskett's Star (PS; HR2420, HD47129, V640 Mon) that were recorded at the Dominion Astrophysical Observatory (DAO) have been digitized with a flatbed scanner. Many of the spectra were recorded during campaigns in 1922 and 1937, and sample wavelengths between 0.39 and 0.50um. Spectra of poor quality are identified. Mean spectra near orbital phases 0.25 and 0.75 match many characteristics of synthetic spectra, although Hgamma and HeI 4388 are exceptions. Evidence is presented that Hgamma was affected by transient activity in 1937, but not in 1922. Emission lines of NIII and HeII move with wavelength in a manner that is consistent with them tracking the motion of the secondary, indicating that an 'f' spectral type designation should be assigned to the secondary. The location of the peak that is associated with the secondary in cross-correlation functions changes with time near phase 0.75, although the mean amplitude of the radial velocity curve of the secondary did not change between the two campaigns. There is also an offset in velocities of the primary measured from Hgamma and HeI 4472 near phase 0.25. The velocity curves of the components suggest a mass ratio that is larger than previous estimates, although uncertainties associated with the spectroscopic features attributed to the secondary, coupled with the wavelength resolution of the spectra, complicate efforts to determine robust masses. We conclude that peculiarities in the radial velocity curves of the components have thus been in place for over a thousand orbital cycles., Comment: To appear in the Astronomical Journal

Commercial flatbed scanners have the potential to deliver a quick and efficient means of capturing the scientific content of spectra recorded on photographic plates. We discuss the digitization of selected spectra in the Dominion Astrophysical Observatory (DAO) photographic plate collection with commercial scanners. In this pilot study, emphasis is placed on assessing if the information on the plates can be recovered using Epson V800 and 12000XL scanners; the more complicated issues associated with the shortcomings of photographic materials, such as correcting for nonlinearity, are deferred to a future study. Spectra of Vega that were recorded over ~4 decades with the DAO 1.8 meter telescope are examined. These spectra sample a range of photographic emulsions, plate preparation techniques, calibration information, observing techniques, and spectrograph configuration. A scanning density of 2400 elements per inch recovers information in the spectra. Differences in the modulation transfer function (MTF) of the two scanners are found, with the Epson 12000XL having a superior MTF. Comparisons with a CCD spectrum of Vega confirm that moderately weak features are faithfully recovered in photographic spectra that have been digitized with the 12000XL scanner. The importance of scanning the full plate to cover the light profile of the target and calibration information is emphasized. Lessons learned from these experiments are also presented.

The properties of the interacting, eccentric orbit binary V1507 Cyg (HD187399) are examined with spectra that cover wavelengths from 0.63 to 0.68um. The spectrum of the brightest star is very similar to that of the B8 I star Beta Ori, although with absorption lines that show sub-structure consistent with a varying tidal field. The bulk of the Halpha emission in the spectrum appears to be associated with the brighter star. Evidence is presented that the period of the system has been stable over timescales of many decades, arguing against large-scale mass transfer at the current epoch. Absorption and emission lines are identified that originate in an expanding asymmetric envelope around the companion, and component masses of 6.4 +/- 0.9 and 14.0 +/- 0.9 solar are found, where the former applies to the brighter star and an inclination of 46 degrees has been assumed. The evolutionary state of V1507 Cyg is then that of a system in which mass transfer has progressed to the point where the mass ratio has been reversed, with the brighter star stripped of much of its initial mass. It is argued that the brighter star is an Alpha Cyg variable, and that it is those light variations that dominate the system light curve. V1507 Cyg is observed at or near the center of a diffuse HI bubble that is detected at 408 and 1420MHz. It is suggested that the eccentric orbit is the result of evolution in a hierarchical system., Comment: Accepted for publication in the Astronomical Journal

Information extracted from the GAIA Data Release 3 is used to examine the stellar contents within projected separations of 10 parsecs from eight close binary systems that are either classical W Serpentis systems or related objects. The goal is to search for remnant star clusters or moving groups with proper motions that are similar to those of the binaries. While some of the binary systems have proper motions that are distinct from those of the majority of stars within the search area, there is still a tendency for W Ser stars to be accompanied by companions with separations on parsec or larger scales. At least three candidate companions are identified within the search area for each system, although in the majority of cases the numbers are much higher. Evidence is presented that SX Cas is near the center of a diffuse cluster. Color-magnitude diagrams (CMDs) of the groupings associated with the binaries are compared with isochrones, and the majority of the groupings are found to have ages in excess of 1 Gyr, indicating that they have an intermediate age. The masses of stars at the main sequence turn-off of the groupings are estimated, and these provide insights into the initial mass of the donor star in each binary system. Images from the WISE Allsky survey are also used to search for circumsystem envelopes. Extended thermal emission is found around six systems in W2 (i.e. ~4.5um) images., Comment: To appear in the Astronomical Journal

Spectra that cover 0.63 - 0.69um with a spectral resolution ~ 17000 are presented of the W Serpentis system V367 Cygni. Absorption lines of FeII and SiII that form in a circumsystem shell are prominent features, and the depths of these are stable with time, suggesting that the shell is smoothly distributed and well-mixed. Further evidence of uniformity comes from modest radial velocity variations measured in the deepest parts of the shell lines. It is suggested that motions previously attributed to rotation of the shell are instead artifacts of contamination from the donor star spectrum. A donor star spectrum is extracted that is consistent with that of an early to mid-A giant. The depths of metallic lines in the donor spectrum vary with orbital phase, suggesting that spot activity covers a large fraction of the surface of that star. A spectrum of the accretion disk that surrounds the second star is also extracted, and similarities are noted with the emission spectra of Herbig Ae/Be stars. In addition to variations with orbital phase, H$\alpha$ changes with time over timescales of no more than two orbits. A tentative detection of HeI 6678 emission is made near primary minimum, but not at other phases. Finally, projected emission from hot dust in and around V367 Cyg is more-or-less symmetric and extends over 28 arcsec, or 0.09 pc at the distance of the system -- V367 Cyg is thus expelling matter into a large volume of the surrounding space., Comment: To appear in the Astronomical Journal

Archival [3.6] and [4.5] images are used to identify and characterize variable stars in the Magellanic-type galaxies Holmberg II, NGC 2366, and IC 2574. Using parametric and non-parametric detection methods, 74 confirmed or suspected long period variables (LPVs) are found. The period distributions of the LPVs in NGC 2366 and IC 2574 are similar. While the period distribution of LPVs in Ho II is uncertain due to small number statistics there appears to be a deficiency of LPVs with periods between 550 and 650 days when compared with NGC 2366 and IC 2574. The LPVs are diffusely distributed on the sky, and do not follow the underlying light from unresolved stars, as expected if episodes of star formation within the past few hundred Myr have occurred throughout the galaxies, including their outer regions. Distances computed for Ho II and NGC 2366 from the period-luminosity relations (PLRs) agree to within ~0.1 magnitudes with those based on the tip of the red giant branch (RGB). Efforts to estimate an LPV-based distance modulus for IC 2574 are complicated by the presence of first overtone pulsators among LPVs with periods ~ 600 days, although the PLR at the long period end is consistent with the distance estimated from the RGB-tip. In addition to the LPVs, 10 candidate sgB[e] or luminous blue variables and 2 candidate red supergiant variables are also identified. Nine candidate sgB[e] stars that do not show evidence of variability are also identified based on their locations in the color-magnitude diagram., Comment: To appear in the Astronomical Journal

Images recorded with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South are combined with archival images from other facilities to search for variable stars in the southern portion of the nearby disk galaxy NGC 247. Fifteen new periodic and non-periodic variables are identified. These include three Cepheids with periods < 25 days, four semi-regular variables, one of which shows light variations similar to those of R CrB stars, five variables with intrinsic visible/red brightnesses and colors that are similar to those of luminous blue variables (LBVs), and three fainter blue variables, one of which may be a non-eclipsing close binary system. The S Doradus instability strip defines the upper envelope of a distinct sequence of objects on the (i', g'-i') color-magnitude diagram (CMD) of NGC 247. The frequency of variability with an amplitude > 0.1 magnitude in the part of the CMD that contains LBVs over the seven month period when the GMOS images were recorded is ~ 0.2. The light curve of the B[e] supergiant J004702.18--204739.9, which is among the brightest stars in NGC 247, is also examined. Low amplitude variations on day-to-day timescales are found, coupled with a systematic trend in mean brightness over a six month time interval., Comment: Accepted for publication in the Astronomical Journal

Observations that span a broad range of wavelengths are used to examine asymmetries in the disk of the nearby late-type spiral galaxy NGC 247. The northern spiral arm is over-luminous at all wavelengths when compared with other parts of the galaxy at similar galactocentric radii, while the density of very luminous red stars in the void that is immediately south of this arm matches that in other parts of the disk at the same galactocentric radius. Two bubbles with spatial extents of many kpc are identified in the disk, and many of the young stars in the southern disk of NGC 247 are located in the walls of one of these structures. Dynamical age estimates of these bubbles coincide with the last large-scale star formation event in the nucleus, suggesting that there was large-scale star formation throughout the disk of NGC 247 a few hundred Myr in the past. Morphological similarities are seen with the classical lop-sided galaxy NGC 4027, and it is concluded that NGC 247 is a significantly lop-sided spiral galaxy. The void in the northern disk is then the area between the main body of the disk and the northern arm viewed in projection. The implications of a lop-sided morphology for NGC 247 in the context of interactions with its nearby starburst galaxy companion NGC 253 are discussed., Comment: To appear in the Astronomical Journal

Long-slit near-infrared (NIR) spectra of the Galactic nuclear star cluster (NSC) are discussed. The spectra sample the major axis of the NSC out to its half light radius. The equivalent widths of NaI2.21um and CaI2.26um outside of the center of the NSC, where light from nuclear bulge stars contributes a large fraction to the total flux, are consistent with solar chemical mixtures. In contrast, the equivalent widths of NaI2.21um and CaI2.26um near the center of the NSC are larger than expected from models with solar chemical mixtures, even after light from the brightest evolved stars is removed. That NaI2.21um and CaI2.26um are deeper than predicted for solar chemical mixtures over a range of evolutionary states is consistent with previous studies that find that the majority of stars near the center of the NSC formed from material that had non-solar chemical mixtures. A spectrum of nebular emission and the youngest stars near the GC is also extracted. The equivalent widths of emission features in the extracted NIR spectrum are similar to those in the nuclear spectrum of NGC 253, and it is argued that this agreement is best achieved if the current episode of star formation near the center of the NSC has been in progress for at least a few Myr., Comment: To appear in the Astronomical Journal

We discuss near-infrared (NIR) slit spectra of six early-type disk galaxies in the Virgo Cluster. While the depth of the CO(2,0) band is consistent with the centers of these galaxies having solar or slightly sub-solar luminosity-weighted metallicities, galaxy-to-galaxy variations in the depth of the NaI 2.21um doublet are found, with NaI2.21um lines in three galaxies (NGC 4491, NGC 4584, and NGC 4620) that are deeper than those predicted for a solar chemical mixture and a solar-neighborhood mass function. Considering the depth of the NaD lines found by Davidge (2018a), the deep NaI2.21um lines are tentatively attributed to a bottom-heavy mass function. This is counter to observed trends between mass function slope and velocity dispersion. Two of the three galaxies with deep NaI2.21um (NGC 4584 and NGC 4620) have Sersic exponents that are consistent with a classical bulge. As for NGC 4491, its central NIR spectrum contains prominent emission lines. The relative strengths of Brgamma and H_2S(1), the presence of [FeII] emission, and the mid-infrared spectral-energy distribution are all consistent with intense recent star formation near the center of that galaxy. Wavelengths that contain the Ballick-Ramsey C_2 band at 1.76um are matched by moderately metal-poor E-MILES model spectra with an age of 2 Gyr. It is concluded that these galaxies have evolved in a cluster environment for at least several Gyr., Comment: To appear in the Astronomical Journal

Spectra that cover wavelengths from 0.6 to 1.1um are used to examine the behavior of emission and absorption features in a contiguous 22 x 300 arcsec region centered on the nearby dwarf galaxy NGC 55. Based on the relative strengths of various emission features measured over spatial scales of many tens of parsecs, it is concluded that the ionization states and sulphur abundances in most of the star-forming regions near the center of NGC 55 are similar. A large star-forming region is identified in the north west part of the disk at a projected distance of ~1 kpc from the galaxy center that has distinct ionization properties. Fossil star-forming regions are also identified using the depth of the near-infrared Ca triplet. One such area is identified near the intersection of the major and minor axes, and it is suggested that this area is a proto-nucleus. The spectra of bright unresolved sources that are blended stellar asterisms, compact HII regions, and star clusters are also discussed. The spectra of some of the HII regions contain Ca triplet absorption lines, signalling a concentration of stars in the resolution element that span many Myr. Six of the unresolved sources have spectroscopic characteristics that are indicative of C stars embedded in intermediate age clusters. The peculiar properties of NGC 55 have been well documented in the literature, and it is argued that these may indicate that NGC 55 is transforming into a dwarf lenticular galaxy., Comment: To appear in The Astronomical Journal

The stellar contents of six intermediate mass early-type disk galaxies in the Virgo cluster are examined using deep long slit spectra. The isophotal and photometric properties of the galaxies at near- and mid-infrared wavelengths are also examined. Characteristic ages and metallicities are found by making comparisons with the strengths of lines measured from model spectra. The light from the central regions of these galaxies at visible/red wavelengths is not dominated by old populations. Rather, the central regions of four galaxies (NGC 4305, NGC 4306, NGC 4497, and NGC 4620) are dominated by populations with ages ~ 1.5 - 3 Gyr. Centrally-concentrated line emission is found in two of the galaxies (NGC 4491 and NGC 4584), and the relative strengths of Halpha and [SII]6746 are consistent with this emission originating in star-forming regions. The disks of these galaxies are dominated by populations that are at least 1 Gyr older than those near the centers, indicating that the quenching of star formation progressed from large radii inwards, and did not occur over a short timescale., Comment: To appear in the Astronomical Journal

Spectra of the intermediate age star cluster NGC 1978 and the dwarf irregular galaxies NGC 55 and NGC 3109 that span the 0.7 to 1.1um wavelength interval are discussed. The NGC 1978 spectra are used to examine stochastic effects on the integrated red light from an intermediate age cluster. The removal of either the brightest M giant or the brightest C star from the co-added NGC 1978 spectrum has minor effects on the equivalent withs of the Ca triplet. The most robust signature of C stars in the integrated cluster spectrum at these wavelengths is the CN band head near 0.79um. The equivalent widths of Ca triplet lines in the NGC 1978 spectrum and in the spectra of individual cluster stars are larger than expected for a scaled-solar abundance system, and it is suggested that these stars have been subject to extra mixing processes. Ca lines weaken with increasing distance from the disk plane in the NGC 55 spectra. Comparisons with models suggest that the red light from NGC 55 is dominated by stars with ages 1 - 2 Gyr, in agreement with star-forming histories (SFHs) obtained from the analysis of CMDs. The NGC 3109 observations sample three different parts of that galaxy but have a low signal-to-noise ratio. Comparisons with models suggest that the light from the NGC 3109 disk at red wavelengths is dominated by RSGs with ages of at most a few tens of Myr, in qualitative agreement with SFHs that are based on photometric measurements.

Images and spectra recorded with the Gemini Multi-Object Spectrograph on Gemini South are used to investigate the stellar content of the open cluster Haffner 16. The (i', g'-i') color-magnitude diagram (CMD) constructed from these data samples the cluster main sequence (MS) and 5 magnitudes of the pre-MS (PMS). The isochrones do not track the PMS on the CMD, in the sense that the PMS has a shallower slope on the CMD than predicted by the models. Still, a dip in star counts that is associated with the relaxation of PMS stars onto the MS is identified near i' = 17. The depth and brightness of this feature - as well as the morphology of the cluster MS on the CMD - are matched by models with a slightly sub-solar metallicity that have an age ~ 20 Myr and a distance modulus of 12.3 +/- 0.2. A light profile of Haffner 16 is constructed in the WISE W1 filter which suggests that the cluster is surrounded by a diffuse stellar halo. Spectra are presented of candidate cluster MS and PMS stars selected according to location on the CMD. The spectra show characteristics that are suggestive of a sub-solar metallicity. Halpha emission is common among objects on the PMS locus on the CMD near i' = 18. It is suggested that the location of the Haffner 16 PMS on the CMD is affected by large-scale cool spot activity, likely induced by rapid stellar rotation., Comment: 30 pages total, with 23 figures. The format differs slightly from the published article

Images and spectra of the open cluster NGC 3105 have been obtained with GMOS on Gemini South. The (i', g'-i') color-magnitude diagram (CMD) constructed from these data extends from the brightest cluster members to g'~23. This is 4 - 5 mag fainter than previous CMDs at visible wavelengths and samples cluster members with sub-solar masses. Assuming a half-solar metallicity, comparisons with isochrones yield a distance of 6.6+/-0.3 kpc. An age of at least 32 Myr is found based on the photometric properties of the brightest stars, coupled with the apparent absence of pre-main sequence stars in the lower regions of the CMD. The luminosity function of stars between 50 and 70 arcsec from the cluster center is consistent with a Chabrier lognormal mass function. However, at radii smaller than 50 arcsec there is a higher specific frequency of the most massive main sequence stars than at larger radii. Photometry obtained from archival SPITZER images reveals that some of the brightest stars near NGC 3105 have excess infrared emission, presumably from warm dust envelopes. Halpha emission is detected in a few early-type stars in and around the cluster, building upon previous spectroscopic observations that found Be stars near NGC 3105. The equivalent width of the NaD lines in the spectra of early type stars is consistent with the reddening found from comparisons with isochrones. Stars with i'~18.5 that fall near the cluster main sequence have a spectral-type A5V, and a distance modulus that is consistent with that obtained by comparing isochrones with the CMD is found assuming solar neighborhood intrinsic brightnesses for these stars., Comment: To appear in The Astrophysical Journal

We discuss images of the star clusters GLIMPSE C01 (GC01) and GLIMPSE C02 (GC02) that were recorded with the Subaru IRCS. Distortions in the wavefront were corrected with the RAVEN adaptive optics (AO) science demonstrator, allowing individual stars in the central regions of both clusters -- where the fractional contamination from non-cluster objects is lowest -- to be imaged. In addition to J, H, and K' images, both clusters were observed through a narrow-band filter centered near 3.05um; GC01 was also observed through two other narrow-band filters that sample longer wavelengths. Stars in the narrow-band images have a FWHM that is close to the telescope diffraction limit, demonstrating that open loop AO systems like RAVEN can deliver exceptional image quality. The near-infrared color magnitude diagram of GC01 is smeared by non-uniform extinction with a dispersion +/- 0.13 magnitudes in A_K. The Red Clump is identified in the K luminosity function (LF) of GC01, and a distance modulus of 13.6 is found. The K LF of GC01 is consistent with a system that is dominated by stars with an age > 1 Gyr. As for GC02, the K LF is flat for K > 16, and the absence of a sub-giant branch argues against an old age if the cluster is at a distance of ~ 7 kpc. Archival SPITZER [3.6] and [4.5] images of the clusters are also examined, and the red giant branch-tip is identified., Comment: To appear in the Astronomical Journal

We present the first results from an extended survey of the Andromeda galaxy (M31) using 41.1 h of observations by Spitzer-IRAC at 3.6 and 4.5$\,\mu$m. This survey extends previous observations to the outer disc and halo, covering total lengths of 4$.\!\!^\circ$4 and 6$.\!\!^\circ$6 along the minor and major axes, respectively. We have produced surface brightness profiles by combining the integrated light from background-corrected maps with stellar counts from a new catalogue of point sources. Using auxiliary catalogues we have carried out a statistical analysis in colour-magnitude space to discriminate M31 objects from foreground Milky Way stars and background galaxies. The catalogue includes 426,529 sources, of which 66 per cent have been assigned probability values to identify M31 objects with magnitude depths of [3.6]$\,=\,$19.0$\,\pm\,$0.2, [4.5]$\,=\,$18.7$\,\pm\,$0.2. We discuss applications of our data for constraining the stellar mass and characterising point sources in the outer radii., Comment: 12 pages, 9 figures, 5 tables; Updated to match published version; minor revisions from v1

We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during sub-arcsec seeing conditions. Absorption features in the spectrum of the star-forming complex are weaker than in the surroundings. An absorption feature is found near 1.78um that coincides with the location of a C2 bandhead. Emission lines of Brgamma, [FeII], and HeI2.06um do not track the NIR continuum light. Pockets of star-forming activity that do not have associated concentrations of red supergiants, and so likely have ages < 8 Myr, are found along the western edge of the complex, and there is evidence that one such pocket contains a rich population of Wolf-Rayet stars. Unless the star-forming complex is significantly more metal-poor than the surroundings, then a significant fraction of its total mass is in stars with ages < 8 Myr. If the present-day star formation rate is maintained then the time scale to double its stellar mass ranges from a few Myr to a few tens of Myr, depending on the contribution made by stars older than ~ 8 Myr. If -- as suggested by some studies -- the star-forming complex is centered on the galaxy nucleus, then the nucleus of NGC 253 is currently experiencing a phase of rapid growth in its stellar mass., Comment: To appear in the Astrophysical Journal

Near-infrared (NIR) spectra that have an angular resolution of ~ 0.15 arcsec are used to examine the stellar content of the central regions of the nearby elliptical galaxy Maffei 1. The spectra were recorded at the Subaru Telescope, with wavefront distortions corrected by the RAVEN Multi-Object Adaptive Optics science demonstrator. The Ballick-Ramsey C_2 absorption bandhead near 1.76 microns is detected, and models in which 10 - 20% of the light near 1.8 microns originates from stars of spectral type C5 reproduce this feature. Archival NIR and mid-infrared images are also used to probe the structural and photometric properties of the galaxy. Comparisons with models suggest that an intermediate age population dominates the spectral energy distribution between 1 and 5 microns near the galaxy center. This is consistent not only with the presence of C stars, but also with the large HBeta index that has been measured previously for Maffei 1. The J-K color is more-or-less constant within 15 arcsec of the galaxy center, suggesting that the brightest red stars are well-mixed in this area., Comment: To appear in The Astrophysical Journal

Images obtained with the Gemini Multi-Object Spectrograph on Gemini South are used to examine the photometric properties and spatial distributions of main sequence (MS) and pre-main sequence (PMS) objects in the star cluster NGC 2401. The data sample several magnitudes fainter than previous studies, and a large population of candidate PMS (cPMS) stars are identified. The cPMS stars are traced out to 2.4 arcmin from the cluster center, and have a flatter spatial distribution than the brightest MS stars near the cluster center. The luminosity function of all MS and candidate PMS stars can be matched by a model that assumes a solar neighborhood mass function, suggesting that NGC 2401 has not yet shed significant numbers of members with masses in excess of 0.5 solar. The frequency of wide binaries among the MS stars is ~3 times higher than among the cPMS stars. It is argued that the difference in the spatial distributions of MS and PMS objects is not the consequence of secular dynamical evolution or structural evolution driven by near-catastrophic mass loss. Rather, it is suggested that the different spatial distributions of these objects is the fossil imprint of primordial sub-clustering that arises naturally if massive stars form preferentially in the highest density central regions of a protocluster., Comment: To appear in the PASP

Long slit spectra recorded with GMOS on Gemini South are used to examine the star-forming history of the lenticular galaxy NGC 5102. Structural and supplemental photometric information are obtained from archival Spitzer [3.6] images. Comparisons with model spectra point to luminosity-weighted metallicities that are consistent with the colors of resolved red giant branch stars in the disk. The nucleus has a luminosity-weighted age at visible wavelengths of ~1 Gyr, and the integrated light is dominated by stars that formed over a time period of only a few hundred Myr. For comparison, the luminosity-weighted ages of the bulge and disk are ~2 Gyr and ~10 Gyr, respectively. The g'-[3.6] colors of the nucleus and bulge are consistent with the spectroscopically-based ages. In contrast to the nucleus, models that assume star-forming activity spanning many Gyr provide a better match to the spectra of the bulge and disk than simple stellar population models. Isophotes in the bulge have a disky shape, hinting that the bulge was assembled from material with significant rotational support. The star-forming histories of the bulge and disk are consistent with the bulge forming from the collapse of a long-lived bar, and it is suggested that the progenitor of NGC 5102 was a barred disk galaxy that morphed into a lenticular galaxy through the buckling of its bar., Comment: To appear in the Astrophysical Journal

Observations of Galactic star clusters and objects in nearby moving groups recorded with Adaptive Optics (AO) systems on Gemini South are discussed. These include observations of open and globular clusters with the GeMS system, and high Strehl L' observations of the moving group member Sirius obtained with NICI. The latter data fail to reveal a brown dwarf companion with a mass in excess of 0.02 solar in an 18 x 18 arcsec^2 area around Sirius A. Potential future directions for AO studies of nearby star clusters and groups with systems on large telescopes are also presented., Comment: Invited review SPIE 9148-11; to appear in SPIE Proceedings

The properties of asymptotic giant branch (AGB) stars in the Local Group galaxy M32 are investigated using ground and space-based observations that span the 1 - 8um wavelength interval, with the goal of demonstrating the utility of infrared observations as probes of stellar content. Comparisons with isochrones indicate that the brightest resolved stars in M32 have ages of a few Gyr, and are younger on average than AGB stars with the same intrinsic brightness in the outer disk of M31. Accounting for stellar variability is shown to be essential for modelling AGB luminosity functions (LFs). Model LFs that assume the star-forming history measured by Monachesi et al. (2012, ApJ, 745, 97) and the variability properties of Galactic AGB stars match both the K and [5.8] LFs of M32. Models also suggest that the slope of the [5.8] LF between M_[5.8] = -8.5 and --10.0 is sensitive to the mix of stellar ages, and a sizeable fraction of the stars in M32 must have an age older than 7 Gyr in order to match the [5.8] LF. The structural properties of M32 in the infrared are also investigated. The effective radii that are computed from near-infrared and mid-infrared isophotes are similar to those measured at visible wavelengths, suggesting that the stellar content of M32 is well-mixed. However, isophotes at radii > 16 arcsec (> 60 parsecs) in the near and mid-infrared are flatter than those at visible wavelengths. The coefficient of the fourth-order cosine term in the fourier expansion of isophotes changes from `boxy' values at r < 16 arcsec to `disky' values at r > 48 arcsec in [3.6] and [4.5]. The mid-infrared colors near the center of M32 do not vary systematically with radius, providing evidence of a well-mixed stellar content in this part of the galaxy., Comment: To appear in The Astrophysical Journal

Images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric seeing by the Gemini Multiconjugate Adaptive Optics System (GeMS) are used to investigate the stellar contents of the young outer Galactic disk clusters Haffner 17, NGC 2401, and NGC 3105. Ages estimated from the faint end of the main sequence (MS) and the ridgeline of the pre-main sequence (PMS) on the (K, J-K) color-magnitude diagrams are consistent with published values that are based on the MS turn-off, with the GSAOI data favoring the younger end of the age range for NGC 2401 in the literature. The mass function (MF) of NGC 2401 is similar to that in the Solar neighborhood, and stars spanning a wide range of masses in this cluster have similar clustering properties on the sky. It is concluded that NGC 2401 is not evolved dynamically. In contrast, the MF of Haffner 17 differs significantly from that in the Solar neighborhood over all masses covered by these data, while the MF of NGC 3105 is deficient in objects with sub-solar masses when compared with the Solar neighborhood. Low mass objects in Haffner 17 and NGC 3105 are also more uniformly distributed on the sky than brighter, more massive, MS stars. This is consistent with both clusters having experienced significant dynamical evolution., Comment: ApJ in press

The photometric properties of main sequence (MS) and pre-main sequence (PMS) stars in the young cluster Haffner 16 are examined using images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric blurring by the Gemini Multi-Conjugate Adapative Optics System (GeMS). A rich population of PMS stars is identified, and comparisons with isochrones suggest an age < 10 Myr assuming a distance modulus of 13.5 (D = 5 kpc). When compared with the solar neighborhood, Haffner 16 is roughly a factor of two deficient in objects with sub-solar masses. PMS objects in the cluster are also more uniformly distributed on the sky than bright MS stars. It is suggested that Haffner 16 is dynamically evolved, and that it is shedding protostars with sub-solar masses. Young low mass clusters like Haffner 16 are one possible source of PMS stars in the field. The cluster will probably evolve on time scales of ~ 100 - 1000 Myr into a diffuse moving group with a mass function that is very different from that which prevailed early in its life., Comment: To appear in the Publications of the Astronomical Society of the Pacific

The stellar content of the open cluster NGC 2437 (Messier 46) is investigated using moderately deep u*,g', and r' MegaCam images. When compared with solar metallicity isochrones, the (g', u'-g') and (r', g'-r') CMDs are consistent with an age log(t_yr) = 8.35 +/- 0.15, a distance modulus 11.05 +/- 0.05, and a color excess E(B-V) = 0.115 +/- 0.035. The r' luminosity function (LF) of main sequence stars in the magnitude range r' < 17 (i.e. masses > 0.8 solar) has a shape that follows solar neighborhood star counts. However, at fainter magnitudes the cluster LF is flat, in contrast with what would be expected from solar neighborhood counts. The clustering properties of stars in NGC 2437 are investigated by examining the two-point angular correlation functions of main sequence stars in different brightness ranges. Main sequence stars fainter than r' = 17 are less centrally concentrated than brighter stars and are found over a larger area of the sky, suggesting that there is a corona of faint main sequence stars around NGC 2437. Based on the flat LF and extended spatial distribution of faint stars, it is concluded that NGC 2437 is actively shedding stars with masses < 0.8 solar., Comment: To appear in the PASP

The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images. Comparisons with isochrones yield an age < 20 Myr for King 12, 20--40 Myr for NGC 7788, and 60 -- 80 Myr for NGC 7790 based on the properties of stars near the main sequence turn-off (MSTO) in each cluster. The reddening of NGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 show breaks that are attributed to the onset of pre-main sequence (PMS) objects, and comparisons with models of PMS evolution yield ages that are consistent with those measured from stars near the MSTO. In contrast, the r' LF of main sequence stars in NGC 7790 is matched to r' = 20 by a model that is based on the solar neighborhood mass function. The structural properties of all three clusters are investigated by examining the two-point angular correlation function of blue main sequence stars. King 12 and NGC 7788 are each surrounded by a stellar halo that extends out to 5 arcmin (~ 3.4 parsecs) radius. It is suggested that these halos form in response to large-scale mass ejection early in the evolution of the clusters, as predicted by models. In contrast, blue main sequence stars in NGC 7790 are traced out to a radius of ~ 7.5 arcmin, with no evidence of a halo. It is suggested that all three clusters may have originated in the same star-forming complex, but not in the same giant molecular cloud., Comment: Astrophysical Journal, in press

We examine the star-forming history (SFH) of the M31 disk during the past few hundred Myr. The luminosity functions (LFs) of main sequence stars at distances R_GC > 21 kpc (i.e. > 4 disk scale lengths) are matched by models that assume a constant star formation rate (SFR). However, at smaller R_GC the LFs suggest that during the past ~10 Myr the SFR was 2 - 3 times higher than during the preceding ~100 Myr. The rings of cool gas that harbor a significant fraction of the current star-forming activity are traced by stars with ages ~100 Myr, indicating that (1) these structures have ages of at least 100 Myr, and (2) stars in these structures do not follow the same relation between age and random velocity as their counterparts throughout the disks of other spiral galaxies, probably due to the inherently narrow orbital angular momentum distribution of the giant molecular clouds in these structures. The distribution of evolved red stars is not azimuthally symmetric, in the sense that their projected density along the north east segment of the major axis is roughly twice that on the opposite side of the galaxy. The north east arm of the major axis thus appears to be a fossil star-forming area that dates to intermediate epochs. Such a structure may be the consequence of interactions with a companion galaxy., Comment: To appear in The Astrophysical Journal

The properties of a stellar grouping that is ~ 3.5 kpc to the north east of the center of M31 is examined. This structure has (1) a surface brightness that is lower than the surrounding disk, (2) a more-or-less round appearance, (3) a size of ~ 300 arcsec (~ 1 kpc), and (4) an integrated brightness M_K = 6.5. It is populated by stars with ages > 100 Myr and J-K colors that tend to be bluer than those of stars in the surrounding disk. Comparisons with model luminosity functions suggest that the star formation rate in this object has changed twice in the past few hundred Myr. Fitting a Sersic function to the light profile reveals a power-law index and effective surface brightness that are similar to those of dwarf galaxies with the same integrated brightness. Two possible origins for this object are considered: (1) it is a heretofore undiscovered satellite of M31 that is seen against/in/through the M31 disk, or (2) it is a fossil star-forming region in the M31 disk., Comment: To appear in The Astrophysical Journal Letters

Images recorded with MegaCam are used to investigate the recent star-forming history (SFH) of the Local Group Sc galaxy M33. The properties of the stellar disk change near R = 8 kpc. Within this radius the star formation rate (SFR) has been constant with time during at least the past 250 Myr, while at larger radii the SFR has declined during this same time period. That the recent SFR in the inner disk has been constant suggests that M33 has evolved in isolation for at least the past ~ 0.5 Gyr, thereby providing a constraint on the timing of any recent interaction with M31. The fractional contribution that young stars make to the total mass of the stellar disk changes with radius, peaking near 8 kpc. Evidence is also presented that the SFR during the past 100 Myr in the southern half of the galaxy has been ~ 0.4 dex higher than in the northern half. Finally, structures with sizes spanning many kpc that contain blue objects - presumably main sequence stars that formed during intermediate epochs - are identified near the disk boundary. It is argued that these are tidal features that were pulled from the main body of M33 and - in some cases - are the fossil remnants of star formation that occured in an extended disk during intermediate epochs., Comment: Accepted for publication in ApJ

We investigate the distribution of bright main sequence stars near the northern edge of the M33 disk. Clustering on sub-kpc scales is seen among stars with ages near 10 Myr, and two large star-forming complexes are identified. Similar large-scale grouping is not evident among stars with ages 100 Myr. These stars are also distributed over a much larger area than those with younger ages, and it is argued that random stellar motions alone, as opposed to orderly motions of the type spurred by large scale secular effects, can re-distribute stars out to distances of at least 2 kpc (i.e. one disk scale length) from their birth places on 100 Myr timescales. Such random motions may thus play a significant role in populating the outer regions of the M33 disk. Finally, it is suggested that - to the extent that the ambient properties of the outer disk mirror those in the main body of the disk - stars in this part of M33 may have formed in star clusters with masses 50 - 250 solar, which is substantially lower than the peak of the solar neighborhood initial cluster mass function., Comment: ApJ (Letters), accepted for publication

Near-infrared images obtained with the CFHT WIRCam are used to investigate the recent history of the nearby Sculptor Group spiral NGC 253. The distribution of stars in the disk is lop-sided, in the sense that the projected density of AGB stars in the north east portion of the disk between 10 and 20 kpc from the galaxy center is ~ 0.5 dex higher than on the opposite side of the galaxy. With the exception of the central 2 kpc, the north east portion of the disk appears to have been the site of the highest levels of star-forming activity in the galaxy during the past ~ 0.1 Gyr. Diffuse stellar structures are found in the periphery of the disk, and the most prominent of these is to the south and east of the galaxy. Bright AGB stars are detected out to 15 kpc above the disk plane, and these are part of a diffusely distributed, flattened extraplanar component. Comparisons between observed and model luminosity functions suggest that the extraplanar regions contain stars that formed throughout much of the age of the Universe. It is suggested that the disk of NGC 253 was disrupted by a tidal encounter with a now defunct companion. The ages of the youngest extraplanar stars suggests that the event that produced the extraplanar population, and presumably induced the starburst, occured within the past ~ 0.2 Gyr., Comment: To appear in the ApJ

The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument being designed for the Thirty Meter Telescope (TMT). IRIS is a combination of an imager that will cover a 16.4" field of view at the diffraction limit of TMT (4 mas sampling), and an integral field unit spectrograph that will sample objects at 4-50 mas scales. IRIS will open up new areas of observational parameter space, allowing major progress in diverse fields of astronomy. We present the science case and resulting requirements for the performance of IRIS. Ultimately, the spectrograph will enable very well-resolved and sensitive studies of the kinematics and internal chemical abundances of high-redshift galaxies, shedding light on many scenarios for the evolution of galaxies at early times. With unprecedented imaging and spectroscopy of exoplanets, IRIS will allow detailed exploration of a range of planetary systems that are inaccessible with current technology. By revealing details about resolved stellar populations in nearby galaxies, it will directly probe the formation of systems like our own Milky Way. Because it will be possible to directly characterize the stellar initial mass function in many environments and in galaxies outside of the the Milky Way, IRIS will enable a greater understanding of whether stars form differently in diverse conditions. IRIS will reveal detailed kinematics in the centers of low-mass galaxies, allowing a test of black hole formation scenarios. Finally, it will revolutionize the characterization of reionization and the first galaxies to form in the universe., Comment: to appear in Proc. SPIE 7735

Deep near-infrared images recorded with NICI on Gemini South are used to investigate the evolved stellar content in the outer regions of the south east quadrant of the spiral galaxy M83. A diffuse population of asymptotic giant branch (AGB) stars is detected outside of the previously identified young and intermediate age star clusters in the outer disk. The brightest AGB stars have M_K > -8, and the AGB luminosity function (LF) is well-matched by model LFs that assume ages < 1 Gyr. The specific star formation rate (SFR) during the past few Gyr estimated from AGB star counts is consistent with that computed from mid-infrared observations of star clusters at similar radii, and it is concluded that the disruption timescale for star clusters in the outer disk is << 1 Gyr. The luminosity function and specific frequency of AGB stars varies with radius, in a manner that is indicative of lower luminosity-weighted ages at larger radii. Modest numbers of red supergiants are also found, indicating that there has been star formation during the past 100 Myr, while the ratio of C stars to M giants is consistent with that expected for a solar metallicity system that has experienced a constant SFR for the past few Gyrs., Comment: Accepted for publication in ApJ

The identification of individual stars in crowded environments using photometric information alone is confounded by source confusion. However, with the addition of spectroscopic information it is possible to distinguish between blends and areas where the light is dominated by a single star using the widths of absorption features. We describe a procedure for identifying locations in kinematically hot environments where the light is dominated by a single star, and apply this method to spectra with 0.1 arcsec angular resolution covering the 2.1 - 2.3 micron interval in the central regions of M32. Targets for detailed investigation are selected as areas of localized brightness enhancement. Three locations where at least 60% of the K-band light comes from a single bright star, and another with light that is dominated by two stars with very different velocities, are identified. The dominant stars are evolving near the tip of the asymptotic giant branch (AGB), and have M5 III spectral type. The lack of a dispersion in spectral-type suggests that the upper AGB within the central arcsec of M32 has a dispersion in J-K of only a few hundreths of a magnitude, in agreement with what is seen at larger radii. One star has weaker atomic absorption lines than the others, such that [M/H] is 0.2 dex lower. Such a difference in metallicity is consistent with the metallicity dispersion inferred from the width of the AGB in M32. The use of line width to distinguish between blends involving many relatively faint stars, none of which dominate the light output, and areas that are dominated by a single intrinsically bright star could be extended to crowded environments in other nearby galaxies., Comment: Accepted for publication in the PASP

The spatial distribution of stars in the nearby S0 galaxy NGC 5102 is investigated using images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope. With the exception of gaps between detector elements, the entire galaxy is surveyed in r' and i', while the J and Ks data extend out to 6 kpc (7 disk scale lengths). A modest population of main sequence (MS) stars with M_V < -3.5 and ages 70 Myr are detected throughout the disk, with the majority located in the southern half of the galaxy. The ratio of C stars to bright M giants is consistent with an overall increase in the star formation rate within the past 1 Gyr. Star-forming activity during the interval 0.1 - 2 Gyr was more centrally concentrated than during the past 100 Myr. The structure of the disk changes near 5 kpc (5.5 disk scale lengths). RSGs and bright AGB stars are traced out to a radius of 14 kpc (15.6 scale lengths) along the southern portion of the major axis, while a tentative detection is also made of bright AGB stars at a projected distance of 16 kpc along the south east minor axis. A large clump of AGB stars that subtends an arcmin is identified to the west of the galaxy center. It is argued that this is the remnant of a companion galaxy that triggered past episodes of elevated star-forming activity., Comment: Accepted for publication in the AJ

Wide-field images obtained with the 3.6 meter Canada-France-Hawaii Telescope are used to investigate the spatial distribution and photometric properties of the brightest stars in the disk of M81 (NGC 3031). With the exception of the central regions of the galaxy and gaps between CCDs, the survey is spatially complete for stars with i' < 24 and major axis distances of 18 kpc. A more modest near-infrared survey detects stars with K < 20 over roughly one third of the disk. Bright main sequence (MS) stars and RSGs are traced out to galactocentric distances of at least 18 kpc. The spatial distribution of bright MS stars tracks emission at far-ultraviolet, mid- and far-infrared wavelengths, although tidal features contain bright MS stars but have little or no infrared flux. The specific frequency of bright MS stars and RSGs, normalized to K-band integrated brightness, increases with radius, indicating that during the past 30 Myr the specific star formation rate (SSFR) has increased with increasing radius. The stellar content of the M81 disk undergoes a distinct change near R ~ 14 kpc, and the luminosity-weighted mean age decreases with increasing radius in the outer regions of the M81 disk., Comment: Accepted for puplication in the ApJ

The stellar content of the debris field around M81 is investigated using deep images obtained with MegaCam on the Canada-France-Hawaii Telescope. Three new concentrations of bright main sequence stars and red supergiants are identified within ~ 20 kpc of M81. These systems have integrated brightnesses M_V ~ -11 and surface brightnesses ~ 27 - 28 mag per arcsec^2 in V. The main sequence turn-offs are consistent with an age of ~ 30 Myr, while the presence of a well-developed red supergiant plume indicates that their stellar content is not coeval, as they also formed stars ~ 100 Myr in the past. The photometric properties of the red supergiants indicate that the young stars in these systems have metallicities that are comparable to those of other objects in the debris field. The HI density near these groupings comfortably exceeds the threshold required to trigger star formation. Based on the close proximity of these objects to M81, coupled with their extended sizes and low inferred masses, it is argued that they will not be long-lived structures, but will probably dissipate within the next ~ 1 Gyr., Comment: 31 pages, including 10 postscript figures; accepted for publication in the PASP

Deep images obtained with MegaCam and WIRCam on the Canada-France-Hawaii Telescope are used to probe the stellar content outside of the central star-forming regions of M82. Stars evolving on the asymptotic giant branch (AGB) are traced along the major axis out to projected distances of 12 kpc, which corresponds to 13 disk scale lengths. The specific frequency (SF) of bright AGB stars in the outer disks of M82 and the Sc galaxy NGC 2403 are identical, suggesting that the specific star formation rates (SFR) in these galaxies during intermediate epochs were similar. This similarity in stellar content, coupled with the presence of an extended stellar disk, is consistent with M82 having been a late-type disk galaxy prior to interacting with M81. Still, there is a paucity of red supergiants (RSGs) in the outer disk of M82 when compared with NGC 2403, indicating that the SFR in the outer regions of M82 during the past ~ 0.1 Gyr has declined dramatically with respect to that in isolated late-type galaxies. A mixture of bright main sequence stars, RSGs, and AGB stars are detected out to minor axis distances of 7 kpc along the outflow. It is suggested that the young and intermediate aged stars in the extraplanar regions formed in structures similar to M82 South, and that these were subsequently disrupted by the tidal action of M82., Comment: 47 pages, including 17 postscript figures. Accepted for publication in AJ

The properties of the brightest resolved stars in an arc that was originally identified by Sun et al. (2005) and is located in the extraplanar regions of M82 are discussed. The stars form an elongated structure that is traced over a projected area of 3.0 x 0.8 kpc. The integrated brightness is M_V ~ -11, while the total stellar mass is between 3 x 10^5 and 2 x 10^6 solar masses. If there is only foreground extinction then the youngest stars have a metallicity Z > 0.008 and an age log(tyears) ~ 7.75; thus, the youngest stars formed at roughly the same time as stars in tidal features that are associated with other M81 Group galaxies. If the arc is dispersing then it will deposit young, chemically enriched stars into the M82 halo., Comment: 11 pages including 3 postscript figures; accepted for publication in ApJ (Letters)

The stellar content of the S0 galaxy NGC 5102 is investigated. A modest population of bright main sequence stars and red supergiants (RSGs) is detected throughout the western portion of the disk, and the star formation rate (SFR) during the past ten million years is estimated to have been 0.02 solar masses per year. RGB stars are traced out to galactocentric distances of 10 kpc, which corresponds to ~ 14 disk scale lengths. A large population of bright asymptotic giant branch (AGB) stars are seen throughout the western portion of the disk, and it is concluded that (1) stars that formed within the past Gyr comprise ~ 20% of the total stellar disk mass, and (2) the SFR during intermediate epochs in the disk of NGC 5102 was at least 1.4 solar masses per year. It is suggested that NGC 5102 was a spiral galaxy that experienced a galaxy-wide episode of enhanced star formation that terminated a few hundred Myr in the past, and that much of its interstellar medium was ejected in an outflow., Comment: To appear in the Astronomical Journal

K-band spectroscopic observations recorded with NIFS+ALTAIR on Gemini North are used to probe the central arcsec of the compact elliptical galaxies NGC 4486B, NGC 5846A, and M32. The angular resolution of these data is ~0.1 arcsec FWHM. The central stellar contents of NGC 4486B and NGC 5846A are similar, in the sense that they occupy the same regions of the (Ca I, 12CO), (Na I, 12CO) and (13CO, 12CO) diagrams. The NGC 4486B and NGC 5846A observations depart from the sequence defined by solar neighborhood giants in the (Na I, 12CO) diagram, in a sense that is consistent with both galaxies having non-solar chemical mixtures. For comparison, the M32 data is consistent with a chemical enrichment history like that in the Galactic disk; M32 could not have formed from the stripping of a larger elliptical galaxy. The behaviour of the near-infrared line indices as a function of radius is also investigated. The radial gradients that are present in NGC 4486B and NGC 5846A at large radii break down or reverse within the central few tenths of an arcsec. Evidence is presented that the nuclear regions of NGC 4486B and NGC 5846A harbour intermediate age populations., Comment: Accepted for publication in the Astrophysical Journal

Deep r' and i' images obtained with GMOS on Gemini South are used to probe the bright stellar content in the outer regions of NGC 5253 and ESO269-G058. Red giant branch (RGB) stars are traced out to a distance of 8 kpc along the major axis of NGC 5253, and 6 kpc in ESO269-G058. The outer regions of both galaxies are metal-poor; RGB stars located between projected major axis distances of 2 and 4 kpc in NGC 5253 have [Fe/H] ~ -1, whereas RGB stars in the corresponding portion of ESO269-G058 have [Fe/H] ~ -1.8. Stars with metallicities that differ from the mean by more than a few tenths of a dex make only a modest contribution to the stellar content in the outer regions of both galaxies. A population of bright asymptotic giant branch (AGB) stars is seen in both galaxies. Roughly 1 - 10% of the stellar mass of NGC 5253 may have formed during the past few hundred million years, and it is suggested that the progenitors of the two recent SN Ia in this galaxy may have formed at this time. It is argued that the current episodes of star formation in NGC 5253 and ESO269-G058 may have been triggered up to ~ 1 Gyr in the past. Finally, a distance modulus is computed for each galaxy based on the brightness of the RGB-tip, and the results are 27.48 +/- 0.14 for NGC 5253, and 27.93 +/- 0.18 for ESO269-G058., Comment: 36 pages, including 11 postscript pages. Astronomical Journal in press

Wide field images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope are used to probe the spatial distribution of young stars in the Sc galaxy NGC 2403. Bright main sequence stars and blue supergiants are detected out to projected galactocentric distances of ~14 kpc (~7 disk scale lengths) along the major axis. The star formation rate (SFR) in the disk of NGC 2403 during the past 10 Myr has been 1 solar masses per year based on the number of bright main sequence stars. The radially-averaged number density of red supergiants (RSGs) per unit r-band surface brightness is constant throughout the disk, indicating that (1) RSGs follow the integrated r-band light, and (2) the SFR per unit mass has been constant with radius when averaged over time scales of a few tens of millions of years. The mean color of RSGs varies with galactocentric distance, suggesting that there is a metallicity gradient among recently formed stars. A comparison of the radially-averaged number density of bright main sequence stars also indicates that the SFR per unit stellar mass in NGC 2403 has been ~3 times higher than in NGC 247 during recent epochs, and this is in rough agreement with what would be predicted from the far infrared fluxes of these galaxies. Finally, the data are used to investigate the extraplanar regions of NGC 2403. A population of M giants with peak brightness M_K = -8 is detected at projected distances between 12 and 14 kpc above the disk plane, and six new globular cluster candidates are identified., Comment: 49 pages, including 17 figures. To appear in ApJ

Near-infrared images are used to investigate the brightest red stars in the disk of the nearby spiral galaxy M81. Red supergiants (RSGs) form a well-defined sequence on the color-magnitude diagrams (CMDs) that peaks near M_K = -11.5; RSGs with this peak brightness are seen throughout all fields that were studied, indicating that star formation occured over a large part of the M81 disk only ~ 10 Myr in the past. The number of RSGs per unit integrated K-band light is compared at various locations in the disk. We conclude that star-forming activity in M81 during the past 10 - 25 Myr (1) was distributed over a larger fraction of the disk than it is at the present day, and (2) was not restricted to a given radial interval, but was distributed in a manner that closely followed the stellar mass profile. Star counts indicate that the mean SFR of M81 between 10 and 25 Myr in the past was ~ 0.1 solar masses per year, which is not greatly different from the present day SFR estimated from Halpha and FUV emission., Comment: 21 pages of text and 7 postscript figures; to appear in the PASP

Broad- and narrow-band images covering the 1 - 4um wavelength interval are used to investigate the properties of the brightest AGB stars in the Local Group galaxy M32. The brightest AGB stars near the center of M32 have peak M_L' brightnesses and K-L' colors that are similar to those of luminous AGB stars in the Galactic disk, while the density of bright AGB stars per unit visible and near-infrared surface brightness is found to be constant out to projected major axis distances of 1 kpc. The J-K color distribution of bright AGB stars throughout much of the galaxy is consistent with that of a single population of AGB stars, the majority of which are long period variables, having a common metallicity and age. Thus, these data do not support spectroscopic studies that find an age gradient in M32. The well-mixed AGB content of M32 is consistent with tidal stirring. The stellar content of M32 is compared with that of the M31 bulge. While the peak K-band brightnesses of AGB stars in the two systems agree to within a few tenths of a magnitude, M32 contains more bright AGB stars per unit integrated brightness than the outer bulge of M31., Comment: 35 pages of text and 20 ps figures; to appear in the AJ

Images obtained with NIRI on the Gemini North telescope are used to investigate the photometric properties of the central regions of M31 in the 3 - 5 micron wavelength range. The light distribution in the central arcsecond differs from what is seen in the near-infrared in the sense that the difference in peak brigh tness between P1 and P2 is larger in M' than in K'; no obvious signature of P3 is dete cted in M'. These results can be explained if there is a source of emission that contributes ~ 20% of the peak M' light of P1 and has an effective temperature of no more than a few hundred K that is located between P1 and P2. Based on the red K-M' color of this source, it is suggested that the emission originates in a circumstellar dust shell surrounding a single bright AGB star. A similar bright source that is ~ 8 arcsec from the center of the galaxy is also detected in M'. Finally, the (L', K-L') color-magnitude diagram of unblended stars shows a domin ant AGB population with photometric characteristics that are similar to those of the most luminous M giants in the Galactic bulge., Comment: To appear in the Astronomical Journal

The stellar content of the spiral galaxy NGC 247 is investigated. The main sequence turn-off (MSTO) in the inner 12 kpc of the disk corresponds to an age of 6 Myr. A mean star formation rate (SFR) of 0.1 solar masses per year during the past 16 Myr is computed from star counts. The color of the red supergiant plume does not change with radius, suggesting that the mean metallicity of young stars does not vary by more than 0.1 dex. The number of bright main sequence stars per local stellar mass density climbs towards larger radii out to a distance of 12 kpc; the scale lengths that characterize the radial distributions of young and old stars in the disk thus differ. The density of bright main sequence stars with respect to projected HI mass gradually drops with increasing radius. The population of very young stars disappears in the outer disk; the MSTO at galactocentric radii between 12 and 15 kpc corresponds to 16 Myr, while between 15 and 18 kpc the age is > 40 Myr. Red giant branch (RGB) stars are resolved at a projected minor axis galactocentric distance of 12 kpc. There is a broad spread in metallicity among the RGB stars, with a mean [M/H] = -1.2. The RGB-tip occurs at i' = 24.5 +/- 0.1, indicating that the distance modulus is 27.9 +/- 0.1. Luminous AGB stars with an age 3 Gyr are also seen in this field., Comment: Includes 16 eps figures; to appear in the Astrophysical Journal

Broad-band near-infrared images are used to probe the photometric properties of the brightest asymptotic giant branch (AGB) stars within 2 arcminutes of the centers of the dwarf elliptical galaxies NGC 147, NGC 185, and NGC 205. Based on the peak brightness and color of the M giant sequences, ages of 1 Gyr and 0.1 Gyr are predicted for the most recent significant star forming events in NGC 185 and NGC 205, respectively. The brightest AGB stars in NGC 147 indicate that the most recent significant star-forming activity in that galaxy occured \~3 Gyr in the past. The specific frequency of C stars outside of the areas of most recent star formation is found to agree in all three galaxies. The fractional contribution made by C stars to the total AGB light in the K-band is found to be highest in NGC 147 and lowest in the central regions of NGC 205, which is qualitatively consistent with model predictions. The fractional contribution that C stars make to the total K-band light is found to be constant both within and between galaxies, with C stars contributing 2% of the total K-band light. It is concluded that, when averaged over timescales of a few Gyr, these galaxies have turned similar fractions of gas and dust, normalised according to total galaxy mass, into stars., Comment: To appear in the Astronomical Journal

Near-infrared images have been used to search for bright globular clusters near the center of the elliptical galaxy Maffei 1. The number of objects in various radial intervals from the center of Maffei 1 are compared with the number density of sources in two control fields, and we find an excess of 31 +/- 11 objects with K between 16.6 and 18.0 in an annulus between 20 and 90 arcsec from the galaxy center. At radii in excess of 90 arcsec the ability to find clusters is frustrated by statistical noise in the foreground star population. It is demonstrated that the globular clusters located within 90 arcsec of the center of Maffei 1 span a range of near-infrared colors that are at least as great as that which is seen among M31 clusters; some of the clusters appear to have colors that are consistent with them being very young. The specific globular cluster frequency within 90 arcsec of the center of Maffei 1 is S_N = 1.3 +/- 0.6 if the distance modulus is 28.1 +/- 0.2 and A_V = 4.7 +/- 0.2. The specific cluster frequency of Maffei 1 is thus similar to that of other nearby field elliptical galaxies., Comment: 34 pages, including 10 eps figures; To appear in the PASP