Search Publications
Evolution of Early-Type Galaxies in Distant Clusters: The Fundamental Plane from Hubble Space Telescope Imaging and Keck Spectroscopy
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +2 more
We present new results on the fundamental plane of galaxies in two rich clusters, Cl 1358+62 at z = 0.33 and MS 2053-04 at z = 0.58, based on Keck and Hubble Space Telescope observations. Our new data triple the sample of galaxies with measured fundamental plane parameters at intermediate redshift. The early-type galaxies in these clusters define …
Hubble Space Telescope Faint Object Spectroscope Spectroscopy of Localized Chemical Enrichment from Massive Stars in NGC 5253
Kobulnicky, Henry A.; Skillman, Evan D.; Walsh, J. R. +2 more
Optical and ultraviolet spectroscopy obtained with the Hubble Space Telescope Faint Object Spectrograph at three locations in the central H II complex of the amorphous starburst galaxy NGC 5253 confirms an apparent area of enhanced nitrogen abundance seen in ground-based studies. At two positions, N appears enhanced by a factor of 3 [log (N/O) = -…
The EXOSAT Data on GX 339-4: Further Evidence for an ``Intermediate'' State
Méndez, Mariano; van der Klis, Michiel
We have studied the fast timing and spectral behavior of the black hole candidate (BHC) GX 339-4 using all 1-20 keV EXOSAT ME data: the 1983 July, 1984 March, 1984 May, and 1985 April observations. In 1985 April, GX 339-4 was in a weak low state (0.03 × 10-9 ergs cm-2 s-1, 2-10 keV). The X-ray spectrum was a hard p…
Quasar Absorbing Galaxies at z <~ 1: Deep Imaging and Spectroscopy in the Field of 3C 336
Dickinson, Mark; Steidel, Charles C.; Sembach, Kenneth R. +2 more
We present very deep WFPC2 images and FOS spectroscopy from the Hubble Space Telescope (HST) together with numerous supporting ground-based observations of the field of the quasar 3C 336 (zem = 0.927). The observations are designed to investigate the nature of galaxies producing metal-line absorption systems in the spectrum of the QSO. …
Infrared Spectroscopy of Dust in the Diffuse Interstellar Medium toward Cygnus OB2 No. 12
de Graauw, Th.; Prusti, T.; van Dishoeck, E. F. +7 more
Observations made with the short-wavelength spectrometer of the Infrared Space Observatory are used to investigate the composition of interstellar dust in the line of sight to Cygnus OB2 No. 12, commonly taken as representative of the diffuse (low-density) interstellar medium. Results are compared with data for the Galactic center source Sgr A*. N…
A Comparison of Direct and Indirect Mass Estimates for Distant Clusters of Galaxies
Smail, Ian; Ellis, Richard S.; Dressler, Alan +4 more
We present weak lensing results for 12 distant clusters determined from images obtained with the refurbished Hubble Space Telescope. We detect the signature of gravitational lensing in 11 of the 12 clusters; the clusters span nearly 1 order of magnitude in lensing strength. The sample thus provides an excellent database for correlating direct mass…
SBS 0335-052, A Probable Nearby Young Dwarf Galaxy: Evidence Pro and Con
Chaffee, Frederic H.; Izotov, Yuri I.; Foltz, Craig B. +3 more
The results of Multiple Mirror Telescope spectrophotometry of the extremely low metallicity blue compact galaxy (BCG) SBS 0335-052 (SBS--the Second Byurakan Survey) are presented. The oxygen abundance in the central, brightest part of the galaxy is found to be 12 + log (O/H) = 7.33 +/- 0.01, only slightly greater than the oxygen abundance in the m…
Self-consistent Thermal Accretion Disk Corona Models for Compact Objects. II. Application to Cygnus X-1
Begelman, Mitchell C.; Wilms, Joern; Dove, James B. +1 more
We apply our self-consistent accretion disk corona (ADC) model, with two different geometries, to the broadband X-ray spectrum of the black hole candidate Cygnus X-1. As shown in a companion paper, models in which the Comptonizing medium is a slab surrounding the cold accretion disk cannot have a temperature higher than about 140 keV for optical d…
White Dwarfs in Globular Clusters: Hubble Space Telescope Observations of M4
Bond, Howard E.; Ibata, Rodrigo A.; Stetson, Peter B. +11 more
Using WFPC2 on the Hubble Space Telescope, we have isolated a sample of 258 white dwarfs (WDs) in the Galactic globular cluster M4. Fields at three radial distances from the cluster center were observed, and sizable WD populations were found in all three. The location of these WDs in the color-magnitude diagram, their mean mass of 0.51(+/-0.03) M<…
Dynamics of Broad Emission-Line Region in NGC 5548: Hydromagnetic Wind Model versus Observations
Korista, Kirk T.; Blandford, Roger D.; Bottorff, Mark +1 more
We analyze the results of long-term observations of the broad-line region (BLR) in the Seyfert 1 galaxy NGC 5548 and provide a critical comparison with the predictions of a hydromagnetically driven outflow model of Emmering, Blandford, & Shlosman. We use this model to generate a time series of C IV line profiles that have responded to a time-v…