Search Publications
On the Origin of Intrinsic Narrow Absorption Lines in z<~1 QSOS
Charlton, Jane C.; Brandt, W. N.; Churchill, Christopher W. +3 more
We present an exhaustive statistical analysis of the associated (Δvabs<5000 km s-1), high-ionization (C IV, N V, O VI) narrow absorption line (NAL) systems in a sample of 59 QSOs defined from the Hubble Space Telescope (HST) QSO Absorption Line Key Project. The goals of the research were twofold: (1) to determine the frequ…
Luminosity Evolution of Field Early-Type Galaxies to Z=0.55
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +1 more
We study the fundamental plane (FP) of field early-type galaxies at intermediate redshift, using Hubble Space Telescope Wide Field Planetary Camera 2 observations and deep Keck spectroscopy. Structural parameters and internal velocity dispersions are measured for 18 galaxies at 0.15<z<0.55. Rest-frame M/LB ratios are determined fr…
Deep Hubble Space Telescope Imaging of IC 1613. I. Variable Stars and Distance
Dolphin, Andrew E.; Skillman, Evan D.; Saha, A. +6 more
We present WFPC2 VI photometry of a field in the halo of IC 1613, finding 13 RR Lyrae stars and 11 Cepheids. Our photometry of the red giant branch tip and red clump is used to derive distances to IC 1613, which are consistent with each other and with distances based on the variable stars. We compare these values with similarly measured distances …
A Low Global Star Formation Rate in the Rich Galaxy Cluster AC 114 at z=0.32
Smail, Ian; Glazebrook, Karl; Balogh, Michael L. +3 more
We present the results of a wide-field survey for Hα-emitting galaxies in the cluster AC 114 at z=0.32. Spectra centered on Hα at the cluster redshift have been obtained for 586 galaxies to Itot~22 out to a radius of ~2 h-150 Mpc. At most, only ~10% of these were found to be Hα-emitting cluster members. These objec…
Models for Multiband Infrared Surveys
Xu, Cong; Shupe, David L.; Lonsdale, Carol J. +2 more
Empirical ``backward'' galaxy evolution models for IR bright galaxies are constrained using multiband IR surveys. A new Monte Carlo algorithm is developed for this task. It exploits a large library of realistic spectral energy distributions (SEDs) of 837 local IR galaxies (IRAS 25 µm selected) from the UV (1000 Å) to the radio (20 cm), inclu…
The Statistical and Physical Properties of the Low-Redshift LYα Forest Observed with the Hubble Space Telescope/STIS
Tripp, Todd M.; Davé, Romeel
We examine the Lyα absorber population at z<0.3 detected in spectra of the quasars PG 0953+415 and H1821+643 taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We compare their statistical properties to those in carefully constructed mock quasar spectra drawn from a cosmological hydrodynamic simulation of a…
Far-Ultraviolet Spectroscopy of the Intergalactic and Interstellar Absorption toward 3C 273
Sembach, Kenneth R.; Savage, Blair D.; Shull, J. Michael +2 more
We present Far Ultraviolet Spectroscopic Explorer observations of the molecular, neutral atomic, weakly ionized, and highly ionized components of the interstellar and intergalactic material toward the quasar 3C 273. We identify Lyβ absorption in eight of the known intergalactic Lyα absorbers along the sight line with rest-frame equivalent widths W…
Heavy X-Ray Absorption in Soft X-Ray-weak Active Galactic Nuclei
Brandt, W. N.; Elvis, M.; Gallagher, S. C. +4 more
Recent ROSAT studies have identified a significant population of active galactic nuclei (AGNs) that are notably faint in soft X-rays relative to their optical fluxes. Are these AGNs intrinsically X-ray weak or are they highly absorbed? Brandt, Laor, & Wills have systematically examined the optical and UV spectral properties of a well-defined s…
A Spatially Resolved, Semiempirical Model for the Extended Atmosphere of α Orionis (M2 Iab)
Harper, Graham M.; Brown, Alexander; Lim, Jeremy
We have constructed a detailed mean density and temperature model for the extended outer atmosphere of the O-rich supergiant Betelgeuse (α Ori [M2 Iab]), which extends from 1.0 to 10.0 stellar radii. A one-dimensional model is based on fitting NRAO1 VLA centimeter visibility data, and two-dimensional models are constructed using the intensity cont…
Oxygen in the Very Early Galaxy
Basri, Gibor; Israelian, Garik; Rebolo, Rafael +4 more
Oxygen abundances in a sample of ultra-metal-poor subdwarfs have been derived from measurements of the oxygen triplet at 7771-5 Å and OH lines in the near-UV performed in high-resolution and high signal-to-noise ratio spectra obtained with WHT/UES, Keck I/HIRES, and VLT/UVES. Our Fe abundances were derived in LTE and then corrected for non-LTE (NL…