Search Publications
Internal Color Properties of Resolved Spheroids in the Deep Hubble Space Telescope Advanced Camera for Surveys Field of UGC 10214
Ford, H. C.; Infante, L.; Zheng, W. +31 more
We study the internal color properties of a morphologically selected sample of spheroidal galaxies taken from the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Early Release Observation program of UGC 10214 (``the Tadpole''). By taking advantage of the unprecedented high resolution of the ACS in this very deep data set, we are abl…
Magnetic Field, Hα, and RHESSI Observations of the 2002 July 23 Gamma-Ray Flare
Krucker, Säm; Wang, Haimin; Yurchyshyn, Vasyl +2 more
In this paper we examine two aspects of the 2002 July 23 gamma-ray flare by using multiwavelength observations. First, the data suggest that the interaction of the erupted field with an overlying large-scale coronal field can explain the offset between the gamma-ray and the hard X-ray sources observed in this event. Second, we pay attention to rap…
Accurate X-Ray Position of the Anomalous X-Ray Pulsar XTE J1810-197 and Identification of Its Likely Infrared Counterpart
Covino, S.; Campana, S.; Mereghetti, S. +13 more
We report the accurate subarcsecond X-ray position of the new anomalous X-ray pulsar (AXP) XTE J1810-197, derived with a Chandra High Resolution Camera Target of Opportunity observation carried out in 2003 November. We also report the discovery of a likely IR counterpart based on a Very Large Telescope (IR band) Target of Opportunity observation c…
The Extinction Law in High-Redshift Galaxies
Kochanek, C. S.; Muñoz, J. A.; Falco, E. E. +2 more
We estimate the dust extinction laws in two intermediate-redshift galaxies. The dust in the lens galaxy of LBQS 1009-0252, which has an estimated lens redshift of zl~=0.88, appears to be similar to that of the SMC, with no significant feature at 2175 Å. Only if the lens galaxy is at a redshift of zl~=0.3, which is completely …
The Properties and Evolution of the Highly Ionized Gas in MR 2251-178
Kaspi, Shai; Nandra, Kirpal; Turner, T. J. +3 more
We present the first XMM-Newton observations of the radio-quiet quasar MR 2251-178 obtained in 2000 and 2002. The EPIC pn spectra show a power-law continuum with a slope of Γ=1.6 at high energies absorbed by at least two warm absorbers (WAs) intrinsic to the source. The underlying continuum in the earlier observation shows a ``soft excess'' at low…
The Radio Continuum of the Metal-deficient Blue Compact Dwarf Galaxy SBS 0335-052
Hunt, Leslie K.; Thuan, Trinh X.; Ulvestad, James S. +1 more
We present new Very Large Array observations at five frequencies, from 1.4 to 22 GHz, of the extremely low metallicity blue compact dwarf SBS 0335-052. The radio spectrum shows considerable absorption at 1.49 GHz and a composite thermal plus nonthermal slope. After fitting the data with a variety of models, we find the best-fitting geometry to be …
Three-dimensional Inversion of Time-Distance Helioseismology Data: Ray-Path and Fresnel-Zone Approximations
Kosovichev, A. G.; Birch, A. C.; Zhao, J. +1 more
Time-distance helioseismology has provided important new insight into the subphotospheric structure and dynamics of sunspots, active regions, supergranular cells, and large-scale flows. These inferences have been made by using either the ray-path or Fresnel-zone approximations. We present inversion results of travel-time perturbations of wavepacke…
The Recent Cluster Formation Histories of NGC 5253 and NGC 3077: Environmental Impact on Star Formation
Conselice, Christopher J.; Calzetti, Daniela; Gallagher, John S., III +2 more
We present multicolor photometry of bright star cluster candidates in the nearby starburst galaxies NGC 3077 and NGC 5253, observed with the Hubble Space Telescope Wide Field Planetary Camera 2 in both broadband (F300W, F547M, and F814W) and narrowband (F487N and F656N) filters. By comparing the photometry with theoretical population synthesis mod…
X-Ray Observations of the Compact Source in CTA 1
Hughes, John P.; Slane, Patrick; Gaensler, Bryan M. +3 more
We have studied the point source RX J0007.0+7302, at the center of supernova remnant CTA 1, using the X-Ray Multi-mirror Mission (XMM-Newton). The X-ray spectrum of the source is consistent with that of a neutron star and is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar c…
New Perspectives on the X-Ray Emission of HD 104237 and Other Nearby Herbig Ae/Be Stars from XMM-Newton and Chandra
Skinner, Stephen L.; Güdel, Manuel; Audard, Marc +1 more
The origin of the X-ray emission from Herbig Ae/Be stars is not yet known. These intermediate-mass pre-main-sequence stars lie on radiative tracks and are not expected to emit X-rays via solar-like magnetic processes, nor are their winds powerful enough to produce X-rays by radiative wind shocks as in more massive O-type stars. The emission could …