Search Publications
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…
High-Resolution Spectroscopy of FU Orionis Stars
Herbig, G. H.; Duemmler, R.; Petrov, P. P.
High-resolution spectroscopy was obtained of the FU orionis stars FU Ori and V1057 Cyg between 1995 and 2002 with the SOFIN spectrograph at the Nordic Optical Telescope and with HIRES at Keck I. During these years FU Ori remained about 1 mag (in B) below its 1938-39 maximum brightness, but V1057 Cyg (B~10.5 at peak in 1970-1971) faded from about 1…
Discovery of Early Optical Emission from GRB 021211
Peterson, B. A.; Price, P. A.; Harrison, F. A. +11 more
We report our discovery and early-time optical, near-infrared, and radio wavelength follow-up observations of the afterglow of the gamma-ray burst GRB 021211. Our optical observations, beginning 21 minutes after the burst trigger, demonstrate that the early afterglow of this burst is roughly 3 mag fainter than the afterglow of GRB 990123 at simila…
Low-Redshift Damped Lyα Galaxies toward the Quasars B2 0827+243, PKS 0952+179, PKS 1127-145, and PKS 1629+120
Turnshek, David A.; Rao, Sandhya M.; Bergeron, Jacqueline +3 more
We present optical and near-infrared ground-based imaging results on four low-redshift damped Lyα (DLA) galaxies. The corresponding DLA systems were discovered in our Hubble Space Telescope spectroscopic surveys for DLA lines in known strong Mg II absorption-line systems toward the quasars B2 0827+243 (zDLA=0.525), PKS 0952+179 (zD…