Search Publications
The Cosmic Evolution of Hard X-Ray-selected Active Galactic Nuclei
Yang, Y.; Capak, P.; Wang, W. -H. +4 more
We use highly spectroscopically complete deep and wide-area Chandra surveys to determine the cosmic evolution of hard X-ray-selected active galactic nuclei (AGNs). For the deep fields, we supplement the spectroscopic redshifts with photometric redshifts to assess where the unidentified sources are likely to lie. We find that the median redshifts a…
A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
Lépine, Sébastien; Shara, Michael M.
The LSPM catalog is a comprehensive list of 61,977 stars north of the J2000 celestial equator that have proper motions larger than 0.15" yr-1 (local-background-stars frame). The catalog has been generated primarily as a result of our systematic search for high proper motion stars in the Digitized Sky Surveys using our SUPERBLINK softwar…
The Centers of Early-Type Galaxies with Hubble Space Telescope. V. New WFPC2 Photometry
Filippenko, Alexei V.; Ho, Luis C.; Gebhardt, Karl +14 more
We present observations of 77 early-type galaxies imaged with the PC1 CCD of the Hubble Space Telescope (HST) WFPC2. ``Nuker-law'' parametric fits to the surface brightness profiles are used to classify the central structure into ``core'' or ``power-law'' forms. Core galaxies are typically rounder than power-law galaxies. Nearly all power-law gala…
Soft X-Ray and Ultraviolet Emission Relations in Optically Selected AGN Samples
Brandt, W. N.; Schneider, Donald P.; Vignali, Cristian +2 more
Using a sample of 228 optically selected active galactic nuclei (AGNs) in the 0.01-6.3 redshift range with a high fraction of X-ray detections (81%-86%), we study the relation between rest-frame UV and soft X-ray emission and its evolution with cosmic time. The majority of the AGNs in our sample (155 objects) have been selected from the Sloan Digi…
The Local Group and Other Neighboring Galaxy Groups
Karachentsev, I. D.
Over the last few years, rapid progress has been made in distance measurements for nearby galaxies based on the magnitude of stars on the tip of the red giant branch. Current CCD surveys with the Hubble Space Telescope (HST) and large ground-based telescopes bring ~10% accurate distances for roughly a hundred galaxies within 5 Mpc. The new data on…
Galactic Globular Cluster Relative Ages
Salaris, Maurizio; Recio-Blanco, Alejandra; Piotto, Giampaolo +5 more
We present accurate relative ages for a sample of 55 Galactic globular clusters. The ages have been obtained by measuring the difference between the horizontal branch and the turnoff in two internally photometrically homogeneous databases. The mutual consistency of the two data sets has been assessed by comparing the ages of 16 globular clusters i…
Herbig Ae/Be Stars in nearby OB Associations
Berlind, Perry; Hartmann, Lee; Calvet, Nuria +3 more
We have carried out a study of the early-type stars in nearby OB associations spanning an age range of ~3-16 Myr, with the aim of determining the fraction of stars that belong to the Herbig Ae/Be class. We studied the B, A, and F stars in the nearby (<=500 pc) OB associations Upper Scorpius, Perseus OB2, Lacerta OB1, and Orion OB1, with members…
Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Makarov, V. V.; Kaplan, G. H.
Useful constraints on the orbits and mass ratios of astrometric binaries in the Hipparcos catalog are derived from the measured proper motion differences of Hipparcos and Tycho-2 (Δµ), accelerations of proper motions (µ˙), and second derivatives of proper motions (µ̈). It is shown how, in some cases, statistical bounds can be esti…
Spectroscopy of Red Giants in the Large Magellanic Cloud Bar: Abundances, Kinematics, and the Age-Metallicity Relation
Cole, Andrew A.; Tolstoy, Eline; Gallagher, John S., III +1 more
We report metallicities and radial velocities derived from spectra at the near-infrared calcium triplet for 373 red giants in a 200 arcmin2 area at the optical center of the LMC bar. These are the first spectroscopic abundance measurements of intermediate-age and old field stars in the high surface brightness heart of the LMC. The metal…
Mapping the Kinematics of the Narrow-Line Region in the Seyfert Galaxy NGC 4151
Gull, T. R.; Kraemer, S. B.; Crenshaw, D. M. +6 more
Using the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS), observations of the [O III] emission from the narrow-line region (NLR) of NGC 4151 were obtained and radial velocities determined. Five orbits of HST time were used to obtain spectra at five parallel slit configurations at a position angle of 58°, with spatial reso…