Search Publications
Discovery of a Binary Active Galactic Nucleus in the Ultraluminous Infrared Galaxy NGC 6240 Using Chandra
Kaastra, J. S.; Burwitz, V.; Hasinger, G. +3 more
Ultraluminous infrared galaxies (ULIRGs) are outstanding due to their huge luminosity output in the infrared, which is predominantly powered by superstarbursts and/or hidden active galactic nuclei (AGNs). NGC 6240 is one of the nearest ULIRGs and is considered a key representative of its class. Here we report the first high-resolution imaging spec…
A Census of the Young Cluster IC 348
Luhman, K. L.; Bouvier, J.; Stauffer, John R. +4 more
We present a new census of the stellar and substellar members of the young cluster IC 348. We have obtained images at I and Z for a 42'×28' field encompassing the cluster and have combined these measurements with previous optical and near-infrared photometry. From spectroscopy of candidate cluster members appearing in these d…
High-Resolution X-Ray Spectroscopic Constraints on Cooling-Flow Models for Clusters of Galaxies
Kaastra, J. S.; Ferrigno, C.; Kahn, S. M. +5 more
We present high-resolution X-ray spectra of 14 putative cooling-flow clusters of galaxies obtained with the Reflection Grating Spectrometer on XMM-Newton. The clusters in the sample span a large range of temperatures and mass deposition rates. Various of these spectra exhibit line emission from O VIII, Ne X, Mg XII and XI, Al XIII and XII, Si XIV …
The Extremely Metal-poor, Neutron Capture-rich Star CS 22892-052: A Comprehensive Abundance Analysis
Beers, Timothy C.; Truran, James W.; Hill, Vanessa +9 more
High-resolution spectra obtained with three ground-based facilities and the Hubble Space Telescope (HST) have been combined to produce a new abundance analysis of CS 22892-052, an extremely metal-poor giant with large relative enhancements of neutron capture elements. A revised model stellar atmosphere has been derived with the aid of a large numb…
The Evolution of the Global Stellar Mass Density at 0<z<3
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C. +1 more
The buildup of stellar mass in galaxies is the consequence of their past star formation and merging histories. Here we report measurements of rest-frame optical light and calculations of stellar mass at high redshift based on an infrared-selected sample of galaxies from the Hubble Deep Field-North. The bright envelope of rest-frame B-band galaxy l…
Axisymmetric Dynamical Models of the Central Regions of Galaxies
Filippenko, Alexei V.; Ho, Luis C.; Gebhardt, Karl +12 more
We present axisymmetric, orbit superposition models for 12 galaxies using data taken with the Hubble Space Telescope (HST) and ground-based observatories. In each galaxy, we detect a central black hole (BH) and measure its mass to accuracies ranging from 10% to 70%. We demonstrate that in most cases the BH detection requires both the HST and groun…
Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble Space Telescope Wide Field Planetary Camera 2
Kirkpatrick, J. Davy; Burgasser, Adam J.; Brown, Michael E. +3 more
We present the discovery of two T dwarf binaries, 2MASS 1225-2739AB and 2MASS 1534-2952AB, identified in a sample of 10 T dwarfs imaged with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2. Companionship is established by the uniquely red F814W-F1042M colors of the binary components, caused by heavily pressure-broadened K I absorpti…
XMM-Newton Observations of the Perseus Cluster. I. The Temperature and Surface Brightness Structure
Böhringer, H.; Churazov, E.; Forman, W. +1 more
We present preliminary results of a XMM-Newton 50 ks observation of the Perseus Cluster that provides an unprecedented view of the central 0.5 Mpc region. The projected gas temperature declines smoothly by a factor of 2 from a maximum value of ~ 7 keV in the outer regions to just above 3 keV at the cluster center. Over this same range, the heavy-e…
A Wide-Field Hubble Space Telescope Study of the Cluster Cl 0024+16 at z = 0.4. I. Morphological Distributions to 5 Mpc Radius
Treu, Tommaso; Smail, Ian; Ellis, Richard S. +5 more
We describe a new wide-field Hubble Space Telescope survey of the galaxy cluster Cl 0024+16 (z~0.4) consisting of a sparsely sampled mosaic of 39 Wide Field Planetary Camera 2 images that extends to a cluster radius of ~5 Mpc. Together with extensive ground-based spectroscopy taken from the literature, augmented with over a hundred newly determine…
A Low-Mass Central Black Hole in the Bulgeless Seyfert 1 Galaxy NGC 4395
Filippenko, Alexei V.; Ho, Luis C.
NGC 4395 is one of the least luminous and nearest known type 1 Seyfert galaxies, and it also lacks a bulge. We present a Hubble Space Telescope (HST) I-band image of its nuclear region and Keck high-resolution (~8 km s-1) echelle spectra containing the Ca II near-infrared triplet. In addition to the unresolved point source, there is a n…