Search Publications
Iron Emission in z~6 QSOS
Korista, Kirk T.; Corbin, Michael R.; Freudling, Wolfram
We have obtained low-resolution near-infrared spectra of three QSOs at 5.7<z<6.3 using the Near-Infrared Camera and Multi-Object Spectrometer on the Hubble Space Telescope. The spectra cover the rest-frame ultraviolet emission of the objects between λrest~1600 and 2800 Å. The Fe II emission-line complex at 2500 Å is clearly detect…
An Estimate of the Sun's ROSAT-PSPC X-Ray Luminosities Using SNOE-SXP Measurements
Ayres, Thomas R.; Judge, Philip G.; Solomon, Stanley C.
Using solar soft X-ray irradiance measurements from the SXP instrument on the SNOE satellite, we relate the solar surface flux densities and their variability to those of stars as measured with the PSPC instrument on ROSAT. We translate SNOE-SXP measurements into equivalent ROSAT-PSPC counts using model spectra calculated from the CHIANTI package.…
Iron Abundance in the Intracluster Medium at High Redshift
Tozzi, P.; Mainieri, V.; Rosati, P. +3 more
We present the analysis of the X-ray spectra of 18 distant clusters of galaxies with redshift 0.3<z<1.3. Most of them were observed with the Chandra satellite in long exposures ranging from 36 to 180 ks. For two of the z>1 clusters, we also use deep XMM-Newton observations. Overall, these clusters probe the temperature range 3keV<~kT&l…
Hubble Space Telescope Paα and 1.9 Micron Imaging of Sagittarius A West
Scoville, N. Z.; Yusef-Zadeh, F.; Stolovy, S. R. +2 more
We present Hubble Space Telescope/NICMOS images at 0.2" resolution (Nyquist-sampled in the central 19") of the H I Paα emission line in a 70''(α)×90''(δ) region of the Galactic center centered on the nonthermal radio source Sgr A*. The majority of the emission arises from ionized gas in the minispiral in the central parsec. P…
The Nuclear Regions of the Seyfert Galaxy NGC 4151: Parsec-Scale H I Absorption and a Remarkable Radio Jet
Mundell, C. G.; Pedlar, A.; Wrobel, J. M. +1 more
Sensitive high angular and linear resolution radio images of the 240 pc radio jet in NGC 4151, imaged at linear resolutions of 0.3-2.6 pc using the VLBA and phased VLA at λ21 cm, are presented and reveal for the first time a faint, highly collimated jet (diameter <~1.4 pc) underlying discrete components, seen in lower resolution MERLIN and VLA …
A Survey for Circumstellar Disks around Young Substellar Objects
Tokunaga, Alan T.; Liu, Michael C.; Najita, Joan
We have completed the first systematic survey for disks around spectroscopically identified young brown dwarfs and very low mass stars. For a sample of 38 very cool objects in IC 348 and Taurus, we have obtained L'-band (3.8 µm) imaging with sufficient sensitivity to detect objects with and without disks. The sample should be free of selecti…
An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. I. Astrometry and Photometry
Heinke, Craig O.; Gilliland, Ronald L.; Edmonds, Peter D. +1 more
We report in this study of 47 Tucanae the largest number of optical identifications of X-ray sources yet obtained in a single globular cluster. Using deep Chandra ACIS-I imaging and extensive Hubble Space Telescope studies with Wide Field Planetary Camera 2 (WFPC2; including a 120 orbit program giving superb V and I images), we have detected optic…
Chandra X-Ray Observatory Observations of the Globular Cluster M28 and Its Millisecond Pulsar PSR B1821-24
Pavlov, George G.; Weisskopf, Martin C.; Tennant, Allyn F. +8 more
We report here the results of the first Chandra X-Ray Observatory observations of the globular cluster M28 (NGC 6626). We detect 46 X-ray sources, of which 12 lie within 1 core radius of the center. We show that the apparently extended X-ray core emission seen with the ROSAT HRI is due to the superposition of multiple discrete sources, for which w…
The Black Hole Masses and Host Galaxies of BL Lacertae Objects
Ho, Luis C.; Barth, Aaron J.; Sargent, Wallace L. W.
We have measured the central stellar velocity dispersion in the host galaxies of 11 BL Lac objects with redshifts z<=0.125. The range of velocity dispersions, ~170-370 km s-1, is similar to that of nearby radio galaxies. Using the correlation between stellar velocity dispersion and black hole mass defined for nearby galaxies, we deri…
Star Formation at z~6: i-Dropouts in the Advanced Camera for Surveys Guaranteed Time Observation Fields
Ford, H. C.; Infante, L.; Zheng, W. +33 more
Using an i-z dropout criterion, we determine the space density of z~6 galaxies from two deep ACS GTO fields with deep optical-IR imaging. A total of 23 objects are found over 46 arcmin2, or ~0.5+/-0.1 objects arcmin-2 down to zAB~27.3 (6 σ), or a completeness-corrected ~0.5+/-0.2 objects arcmin-2 down to…