Search Publications
C II Radiative Cooling of the Diffuse Gas in the Milky Way
Savage, B. D.; Wakker, B. P.; Lehner, N.
The heating and cooling of the interstellar medium (ISM) allow the gas in the ISM to coexist at very different temperatures in thermal pressure equilibrium. The rate at which the gas cools or heats is therefore a fundamental ingredient for any theory of the ISM. The heating cannot be directly determined, but the cooling can be inferred from observ…
Dramatic X-Ray Spectral Variability of the Broad Absorption Line Quasar PG 2112+059
Brandt, W. N.; Chartas, G.; Gallagher, S. C. +3 more
With a 1999 ASCA observation, PG 2112+059 became notable as the first broad absorption line (BAL) quasar found to exhibit a typical radio-quiet quasar X-ray continuum underlying a large amount of intrinsic absorption. We present a recent Chandra ACIS-S3 observation of PG 2112+059 that demonstrates remarkable spectral and luminosity variability sin…
The First Detailed X-Ray Observations of High-Redshift, Optically Selected Clusters: XMM-Newton Results for Cl 1324+3011 at z = 0.76 and Cl 1604+4304 at z = 0.90
Mulchaey, John S.; Postman, Marc; Lubin, Lori M.
We present the first detailed X-ray observations of optically selected clusters at high redshift. Two clusters, Cl 1324+3011 at z=0.76 and Cl 1604+4304 at z=0.90, were observed with XMM-Newton. The opticenter of each cluster is coincident with an extended X-ray source whose emission is detected out to a radius of ~0.5 h-170 M…
Hubble Space Telescope STIS Far-Ultraviolet Observations of the Central Nebulae in the Cooling-Core Clusters A1795 and A2597
Koekemoer, Anton M.; Baum, Stefi A.; Mack, Jennifer +2 more
We present Hubble Space Telescope STIS FUV images of the Lyα and FUV continuum emission of the luminous emission-line nebulae in two cooling-core clusters, A1795 and A2597. The Lyα and FUV continuum emission consist of a diffuse component (~60%) and more compact features (knots and filaments), which lie preferentially along the radio source edges.…
The Progenitor of the Type II-P SN 2004dj in NGC 2403
Bond, Howard E.; Maoz, D.; Ofek, E. O. +4 more
The Type II-P supernova SN 2004dj in the nearby galaxy NGC 2403 occurred at a position coincident with object 96 in the list of luminous stars and clusters in this galaxy published by Sandage in 1984. The coincidence is established definitively through astrometric registration of our ground-based archival images of NGC 2403 with our recent images …
A Possible Explanation for the Size Difference of Red and Blue Globular Clusters
Jordán, Andrés
Most observations of the projected half-light radii of metal-rich globular clusters in a variety of galaxies have shown them to be ~20% smaller than those of their metal-poor counterparts. We show using multimass isotropic Michie-King models that the combined effects of mass segregation and the dependence of main-sequence lifetimes on metallicity …
Measurement of Cosmic Shear with the Space Telescope Imaging Spectrograph
Refregier, Alexandre; Gardner, Jonathan P.; Rhodes, Jason +3 more
Weak lensing by large-scale structure allows a direct measure of the dark matter distribution. We have used parallel images taken with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to measure weak lensing, or cosmic shear. We measure the shapes of 26,036 galaxies in 1292 STIS fields and measure the shear variance at…
Variability of Narrow, Associated Absorption Lines in Moderate- and Low-Redshift Quasars
Charlton, Jane C.; Eracleous, Michael; Ganguly, Rajib +1 more
We present the results of a search for variability in the equivalent widths (EWs) of narrow, associated (|Δv|<=5000 km s-1) absorption lines found in the UV spectra of z<=1.5 quasars. The goal of this search was to use variability as a means of identifying absorption lines arising in gas that is intrinsic to the quasar central eng…
The Hot White Dwarf in the Cataclysmic Variable MV Lyrae
Szkody, Paula; Sion, Edward M.; Hoard, D. W. +4 more
We have obtained the first far-ultraviolet spectrum of the nova-like cataclysmic variable MV Lyrae using the Far Ultraviolet Spectroscopic Explorer (FUSE). We also obtained contemporaneous optical light curves and spectra. All data are from a deep faint accretion state of MV Lyr. We constructed a model for the system using the BINSYN software pack…
Chandra Observations of the Cloverleaf Quasar H1413+117: A Unique Laboratory for Microlensing Studies of a LoBAL Quasar
Agol, E.; Chartas, G.; Gallagher, S. C. +1 more
We present new results uncovered by a reanalysis of a Chandra observation of the gravitationally lensed, low-ionization broad absorption line (LoBAL) quasar H1413+117. Previous analyses of the same Chandra observation led to the detection of a strong, redshifted Fe Kα line from the combined spectrum of all images. We show that the redshifted Fe Kα…