Search Publications
Chandra Reveals the X-Ray Glint in the Cat's Eye
Guerrero, Martín A.; Chu, You-Hua; Gruendl, Robert A. +2 more
We have obtained Chandra ACIS-S observations of NGC 6543, the Cat's Eye Nebula. The X-ray emission from NGC 6543 is clearly resolved into a point source at the central star and diffuse emission confined within the central elliptical shell and two extensions along the major axis. Spectral analysis of the diffuse component shows that the abundances …
Blue Stragglers, Young White Dwarfs, and UV-Excess Stars in the Core of 47 Tucanae
Ferraro, Francesco R.; Paltrinieri, Barbara; Possenti, Andrea +2 more
We used a set of archived Hubble Space Telescope/WFPC2 images to probe the stellar population in the core of the nearby galactic globular cluster (GGC) 47 Tuc. From the ultraviolet (UV) color magnitude diagrams (CMDs) obtained for ~4000 stars detected within the Planetary Camera (PC) field of view we have pinpointed a number of interesting objects…
The White Dwarf Distance to the Globular Cluster 47 Tucanae and its Age
Zoccali, M.; Bragaglia, A.; Rich, R. M. +9 more
We present a new determination of the distance (and age) of the Galactic globular cluster 47 Tucanae (NGC 104) based on the fit of its white dwarf (WD) cooling sequence with the empirical fiducial sequence of local WD with known trigonometric parallax, following the method described by Renzini and collaborators. Both the cluster and the local WDs …
Proper Motions of the HH 111 Jet Observed with the Hubble Space Telescope
Hartigan, Patrick; Bally, John; Reipurth, Bo +2 more
New Hα and [S II] images of the HH 111 jet taken with the Hubble Space Telescope reveal marked proper motions and morphological changes when compared with similar images obtained 4 years earlier. Knots in the jet, which are dominated by emission from nested bow shocks, generally move ballistically, with no evidence for turbulent motions even in re…
A Hubble Space Telescope Lensing Survey of X-Ray Luminous Galaxy Clusters. I. A383
Smith, Graham P.; Smail, Ian; Kneib, Jean-Paul +2 more
We present an analysis of the mass distribution in the core of A383 (z=0.188), one of 12 X-ray luminous galaxy clusters at z~0.2 selected for a comprehensive and unbiased study of the mass distribution in massive galaxy clusters. Deep optical imaging performed by the Hubble Space Telescope (HST) reveals a wide variety of gravitationally lensed fea…
On the Origin of Intrinsic Narrow Absorption Lines in z<~1 QSOS
Charlton, Jane C.; Brandt, W. N.; Churchill, Christopher W. +3 more
We present an exhaustive statistical analysis of the associated (Δvabs<5000 km s-1), high-ionization (C IV, N V, O VI) narrow absorption line (NAL) systems in a sample of 59 QSOs defined from the Hubble Space Telescope (HST) QSO Absorption Line Key Project. The goals of the research were twofold: (1) to determine the frequ…
Luminosity Evolution of Field Early-Type Galaxies to Z=0.55
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +1 more
We study the fundamental plane (FP) of field early-type galaxies at intermediate redshift, using Hubble Space Telescope Wide Field Planetary Camera 2 observations and deep Keck spectroscopy. Structural parameters and internal velocity dispersions are measured for 18 galaxies at 0.15<z<0.55. Rest-frame M/LB ratios are determined fr…
Deep Hubble Space Telescope Imaging of IC 1613. I. Variable Stars and Distance
Dolphin, Andrew E.; Skillman, Evan D.; Saha, A. +6 more
We present WFPC2 VI photometry of a field in the halo of IC 1613, finding 13 RR Lyrae stars and 11 Cepheids. Our photometry of the red giant branch tip and red clump is used to derive distances to IC 1613, which are consistent with each other and with distances based on the variable stars. We compare these values with similarly measured distances …
A Low Global Star Formation Rate in the Rich Galaxy Cluster AC 114 at z=0.32
Smail, Ian; Glazebrook, Karl; Balogh, Michael L. +3 more
We present the results of a wide-field survey for Hα-emitting galaxies in the cluster AC 114 at z=0.32. Spectra centered on Hα at the cluster redshift have been obtained for 586 galaxies to Itot~22 out to a radius of ~2 h-150 Mpc. At most, only ~10% of these were found to be Hα-emitting cluster members. These objec…
Models for Multiband Infrared Surveys
Xu, Cong; Shupe, David L.; Lonsdale, Carol J. +2 more
Empirical ``backward'' galaxy evolution models for IR bright galaxies are constrained using multiband IR surveys. A new Monte Carlo algorithm is developed for this task. It exploits a large library of realistic spectral energy distributions (SEDs) of 837 local IR galaxies (IRAS 25 µm selected) from the UV (1000 Å) to the radio (20 cm), inclu…