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…
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…
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…
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…
Candidate Type II Quasars from the Sloan Digital Sky Survey. III. Spectropolarimetry Reveals Hidden Type I Nuclei
Hall, Patrick B.; Strauss, Michael A.; Brinkmann, J. +7 more
We have conducted spectropolarimetry of 12 type II (obscured) quasar candidates selected from the spectroscopic database of the Sloan Digital Sky Survey on the basis of their emission-line properties. Polarization was detected in all objects, with nine being highly polarized (>3%) and with polarization reaching as high as 17% in two objects. Br…
Confirmation of Errors in Hipparcos Parallaxes from Hubble Space Telescope Fine Guidance Sensor Astrometry of the Pleiades
Soderblom, David R.; Benedict, G. Fritz; McArthur, Barbara +4 more
We present absolute trigonometric parallaxes and relative proper motions for three members of the Pleiades, obtained with the Hubble Space Telescope's Fine Guidance Sensor 1r, a white-light interferometer. We estimate spectral types and luminosity classes of the stars comprising the astrometric reference frame from R~2000 spectra, VJHK photometry,…
Hubble Space Telescope Advanced Camera for Surveys Coronagraphic Imaging of the AU Microscopii Debris Disk
Ford, H. C.; Demarco, R.; Infante, L. +38 more
We present Hubble Space Telescope Advanced Camera for Surveys multicolor coronagraphic images of the recently discovered edge-on debris disk around the nearby (~10 pc) M dwarf AU Microscopii. The disk is seen between r=0.75" and 15" (7.5-150 AU) from the star. It has a thin midplane with a projected FWHM thickness of 2.5-3.5 AU within r<50 AU o…
The Near-Infrared Camera and Multi-Object Spectrometer Ultra Deep Field: Observations, Data Reduction, and Galaxy Photometry
Dickinson, Mark; Franx, Marijn; van Dokkum, Pieter +10 more
This paper describes the observations and data reduction techniques for the version 2.0 images and catalog of the Near-Infrared Camera and Multi-Object Spectrometer Ultra Deep Field (NICMOS UDF) Treasury program. All sources discussed in this paper are based on detections in the combined NICMOS F110W and F160W bands only. The NICMOS images are dri…