Search Publications
Mass Distributions of Hubble Space Telescope Galaxy Clusters from Gravitational Arcs
Bartelmann, Matthias; Meneghetti, Massimo; Comerford, Julia M. +1 more
Although N-body simulations of cosmic structure formation suggest that dark matter halos have density profiles shallower than isothermal at small radii and steeper at large radii, whether observed galaxy clusters follow this profile is still ambiguous. We use one such density profile, the asymmetric Navarro-Frenk-White (NFW) profile, to model the …
Tracing Galaxy Assembly: Tadpole Galaxies in the Hubble Ultra Deep Field
Ryan, R. E.; Hathi, N. P.; Jansen, R. A. +3 more
In the Hubble Ultra Deep Field (HUDF) an abundance of galaxies is seen with a knot at one end plus an extended tail, resembling a tadpole. These ``tadpole galaxies'' appear dynamically unrelaxed-presumably in an early merging stage-where tidal interactions likely created the distorted knot-plus-tail morphology. Here we systematically select tadpol…
Ultraviolet-to-Far-Infrared Properties of Local Star-forming Galaxies
Giavalisco, M.; Leitherer, C.; Armus, L. +5 more
We present the results of a multiwavelength study of nearby galaxies aimed at understanding the relation between the ultraviolet and far-infrared emission in star-forming galaxies. The data set comprises new ultraviolet (from HST STIS), ground-based Hα, and radio continuum observations, together with archival infrared data (from IRAS and ISO). The…
Infrared and Optical Observations of GRB 030115 and its Extremely Red Host Galaxy: Implications for Dark Bursts
Mobasher, Bahram; Garnavich, Peter; Tanvir, Nial +24 more
We present near-infrared (NIR) and optical observations of the afterglow of GRB 030115. Discovered in an infrared search at Kitt Peak 5 hr after the burst trigger, this afterglow is the faintest ever observed in the R band at such an early epoch and exhibits very red colors, with R-K~6. The optical magnitude of the afterglow of GRB 030115 is faint…
An Analysis of Ultraviolet Spectra of Extreme Helium Stars and New Clues to Their Origins
Rao, N. Kameswara; Lambert, David L.; Pandey, Gajendra +1 more
Abundances of about 18 elements including the heavy elements Y and Zr are determined from Hubble Space Telescope Space Telescope Imaging Spectrograph ultraviolet spectra of seven extreme helium stars (EHes): LSE 78, BD +10 2179, V1920 Cyg, HD 124448, PV Tel, LS IV-1 2, and FQ Aqr. New optical spectra of BD +10 2179, V1920 Cyg, and HD 124448 were a…
Flux-Rope Coronal Mass Ejection Geometry and Its Relation to Observed Morphology
St. Cyr, O. C.; Krall, J.
A simple parameterization of a three-dimensional flux rope is used to determine a ``typical flux-rope geometry'' that corresponds to observed flux-rope coronal mass ejection (CME) morphologies (average apparent angular widths) at a leading-edge height of about 5.5 Rsolar. The parameterized flux rope, the curved axis of which is assumed to trace ou…
Two Successive Coronal Mass Ejections Driven by the Kink and Drainage Instabilities of an Eruptive Prominence
Zhang, J.; Chen, P. F.; Wang, J. X. +3 more
We describe a clear case of the initiation of a propagating bright arc and a CME on 2002 December 28, which were associated with an eruptive prominence. In EIT 304 and 195 Å images, a very long filament showed evidence of severe twisting in one of its fragments, which appeared as a prominence on December 26; then, the prominence showed the convers…
FUSE and HST STIS Far-Ultraviolet Observations of AM Herculis in an Extended Low State
Hubeny, Ivan; Gänsicke, Boris T.; Long, Knox S. +1 more
We have obtained FUSE and HST STIS time-resolved spectroscopy of the Polar AM Herculis during a deep low state. The spectra are entirely dominated by the emission of the white dwarf. Both the far-ultraviolet (FUV) flux and the spectral shape vary substantially over the orbital period, with maximum flux occurring at the same phase as during the hig…
Evidence for a Supernova Associated with the X-Ray Flash 020903
Covino, S.; Becker, A. C.; Filippenko, A. V. +24 more
We present ground-based and Hubble Space Telescope optical observations of the X-ray flash (XRF) 020903, covering 300 days. The afterglow showed a very rapid rise in the first day, followed by a relatively slow decay in the next few days. There was a clear bump in the light curve after ~25 days, accompanied by a drastic change in the spectral ener…
Rings and Bent Chain Galaxies in the GEMS and GOODS Fields
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
Twenty-four galaxies with rings or partial rings were studied in the GEMS and GOODS fields out to z~1.4. Most resemble local collisional ring galaxies in morphology, size, and clumpy star formation. Clump ages range from 108 to 109 yr, and clump masses go up to several × 108 Msolar, based on color evolut…