Search Publications
Self-similar Models for the Mass Profiles of Early-Type Lens Galaxies
Keeton, C. R.; Kochanek, C. S.; Rusin, D.
We introduce a self-similar mass model for early-type galaxies and constrain it using the aperture mass-radius relations determined from the geometries of 22 gravitational lenses. The model consists of two components: a concentrated component, which traces the light distribution, and a more extended power-law component (ρ~r-n), which re…
Chandra X-Ray Observations of NGC 1316 (Fornax A)
Fabbiano, G.; Kim, Dong-Woo
We report the results of the Chandra ACIS subarcsecond resolution X-ray observation of the archetypal merger radio galaxy NGC 1316 (Fornax A). We confirm the presence of fine substructures in the hot interstellar medium (ISM). Some of these are likely to result from interaction with the radio jets, while others may be related to a complex intermin…
The Circumstellar Disk of the Butterfly Star in Taurus
Stapelfeldt, Karl R.; Padgett, Deborah L.; Wolf, Sebastian
We present a model of the circumstellar environment of the so-called Butterfly star in Taurus (IRAS 04302+2247). The appearance of this young stellar object is dominated by a large circumstellar disk seen edge-on and the light-scattering lobes above the disk. Our model is based on multiwavelength continuum observations: (1) millimeter maps and (2)…
A Long Look at NGC 3783 with the XMM-Newton Reflection Grating Spectrometer
Rasmussen, Andrew P.; Kahn, Steven M.; Behar, Ehud +5 more
A long 280 ks observation of the Seyfert 1 galaxy NGC 3783 with XMM-Newton is reported. We focus on the oxygen line complex between 17 and 24 Å as measured with the Reflection Grating Spectrometer. Accurate absorption column densities and emission-line fluxes are obtained. We explore several options for the geometry and physical form of the emitti…
Spectroscopic Confirmation of a Substantial Population of Luminous Red Galaxies at Redshifts z>~2
van Dokkum, Pieter G.; Franx, Marijn; Illingworth, Garth D. +10 more
We confirm spectroscopically the existence of a population of galaxies at z>~2 with rest-frame optical colors similar to normal nearby galaxies. The galaxies were identified by their red near-infrared colors in deep images obtained with the Infrared Spectrometer and Array Camera on the Very Large Telescope of the field around the foreground clu…
The Cepheid Distance to NGC 1637: A Direct Test of the Expanding Photosphere Method Distance to SN 1999em
Leonard, Douglas C.; Tanvir, Nial R.; Kanbur, Shashi M. +1 more
Type II-plateau supernovae (SNe II-P) are the classic variety of core-collapse events that result from isolated, massive stars with thick hydrogen envelopes intact at the time of explosion. Their distances are now routinely estimated through two techniques: the expanding photosphere method (EPM), a primary distance-determining method, and the rece…
The Nature of E+A Galaxies in Intermediate-Redshift Clusters
Franx, Marijn; Kelson, Daniel D.; Tran, Kim-Vy H. +2 more
Combining Hubble Space Telescope WFPC2 mosaics with extensive ground-based spectroscopy, we study the nature of E+A galaxies in three intermediate-redshift clusters (z=0.33, 0.58, and 0.83). From a sample of ~500 confirmed cluster members, we isolate 46 E+A candidates to determine the E+A fraction and study their physical properties. Spectral type…
Deep Hubble Space Telescope Imaging of IC 1613. II. The Star Formation History
Dolphin, Andrew E.; Skillman, Evan D.; Cole, Andrew A. +5 more
We have taken deep images of an outlying field in the Local Group dwarf irregular galaxy IC 1613 with the WFPC2 aboard the Hubble Space Telescope in the standard broadband F555W (V, 8 orbits) and F814W (I, 16 orbits) filters. The photometry reaches to V=27.7 (MV=+3.4) and I=27.1 (MI=+2.8) at the 50% completeness level, the de…
Fe II/Mg II Emission-Line Ratio in High-Redshift Quasars
Vestergaard, M.; Dietrich, M.; Appenzeller, I. +1 more
We present results of the analysis of near-infrared spectroscopic observations of six high-redshift quasars (z>~4), emphasizing the measurement of the ultraviolet Fe II/Mg II emission-line strength to estimate the beginning of intense star formation in the early universe. To investigate the evolution of the Fe II/Mg II ratio over a wider range …
Blue Straggler Stars: A Direct Comparison of Star Counts and Population Ratios in Six Galactic Globular Clusters
Ferraro, Francesco R.; Sills, Alison; Paltrinieri, Barbara +2 more
The central regions of six Galactic globular clusters (GGCs) (M3, M80, M10, M13, M92, and NGC 288) have been imaged using HST-WFPC2 and the ultraviolet filters (F255W and F336W). The selected sample covers a large range in both central density (logρ0) and metallicity ([Fe/H]). In this paper, we present a direct cluster-to-cluster compar…