Search Publications
The Abundance of Deuterium in the Warm Neutral Medium of the Lower Galactic Halo
Savage, Blair D.; Lehner, Nicolas; Fox, Andrew +2 more
We use high-resolution ultraviolet spectra to obtain Milky Way interstellar column densities of H I, D I, O I, S II, Fe II, and P II toward the QSO HE 0226-4110 in the Galactic direction l=253.4deg and b=-65.77deg. We obtain D/H=21+8-6 ppm from an analysis of the strong damped Lyα line of H I and the wea…
A Compact Cluster of Massive Red Galaxies at a Redshift of 1.5
Glazebrook, Karl; McCarthy, Patrick J.; Yan, Haojing +15 more
We describe a compact cluster or group of massive red galaxies at z=1.5 discovered in one of the Gemini Deep Deep Survey (GDDS) fields. Deep H-band imaging from the Hubble Space Telescope (HST) reveals a high density of red galaxies associated with a galaxy with a spectroscopic redshift of 1.51. These galaxies have spectral energy distributions (S…
Black Hole Masses and Eddington Ratios of AGNs at z < 1: Evidence of Retriggering for a Representative Sample of X-Ray-selected AGNs
Danese, L.; Ballo, L.; Tozzi, P. +10 more
We estimated black hole masses and Eddington ratios for a sample of X-ray-selected active galactic nuclei (AGNs) in the fields covered by the Great Observatory Origins Deep Survey (GOODS). The spanned ranges in redshift (0.4<z<1) and hard X-ray luminosity (1042<~LX<~4×1043 ergs s-1) allow us …
Variability of Moderate-Luminosity Active Galactic Nuclei at z = 0.36
Treu, Tommaso; Malkan, Matthew A.; Woo, Jong-Hak +2 more
We monitored 13 moderate-luminosity active galactic nuclei at z=0.36 to measure flux variability, explore feasibility of reverberation mapping, and determine uncertainties on estimating black hole mass from single-epoch data. Spectra and images were obtained with approximately weekly cadence for up to 4 months, using the Kast spectrograph on the 3…
The Variation of Magnesium Depletion with Line-of-Sight Conditions
Snow, Theodore P.; Jensen, Adam G.
In this paper we report on the gas-phase abundance of singly ionized magnesium (Mg II) in 44 lines of sight, using data from the Hubble Space Telescope (HST). We measure Mg II column densities by analyzing medium- and high-resolution archival Space Telescope Imaging Spectrograph (STIS) spectra of the 1240 Å doublet of Mg II. We find that Mg II dep…
X-Ray Localization of the Globular Cluster G1 with XMM-Newton
Kong, Albert K. H.
We present an accurate X-ray position of the massive globular cluster G1 obtained using XMM-Newton and the Hubble Space Telescope (HST). The X-ray emission of G1 has been detected recently with XMM-Newton. There are two possibilities for the origin of the X-ray emission: it could be due to either accretion of the central intermediate-mass black ho…
An X-Ray Spectral Analysis of the Central Regions of NGC 4593
Kaiser, Mary Elizabeth; Brenneman, Laura W.; Wilms, Jörn +1 more
We present a detailed analysis of XMM-Newton EPIC-pn data for the Seyfert 1 galaxy NGC 4593. We discuss the X-ray spectral properties of this source, as well as its variations with time. The 0.5-10 keV spectrum shows significant complexity beyond a simple power-law form, with clear evidence existing for a ``soft excess,'' as well as absorption by …
The Star-forming Region NGC 346 in the Small Magellanic Cloud with Hubble Space Telescope ACS Observations. II. Photometric Study of the Intermediate-Age Star Cluster BS 90
Henning, Thomas; Gouliermis, Dimitrios A.; Dolphin, Andrew E. +2 more
We present the results of our investigation of the intermediate-age star cluster BS 90, located in the vicinity of the H II region N66 in the SMC, observed with HST ACS. The high-resolution data provide a unique opportunity for a very detailed photometric study performed on one of the rare intermediate-age rich SMC clusters. The complete set of ob…
Adaptive Optics Imaging of IRAS 18276-1431: A Bipolar Preplanetary Nebula with Circumstellar ``Searchlight Beams'' and ``Arcs''
Sahai, R.; Sánchez Contreras, C.; Le Mignant, D. +2 more
We present high angular resolution images of the post-AGB nebula IRAS 18276-1431 (also known as OH 17.7-2.0) obtained with the Keck II adaptive optics (AO) system in its natural guide star (NGS) mode in the Kp, Lp, and Ms near-infrared bands. We also present supporting optical F606W and F814W HST images as well as …
Chandra and XMM-Newton Discovery of Transient X-Ray Pulsar in the Nearby Spiral Galaxy NGC 2403
Córdova, France A.; Trudolyubov, Sergey P.; Priedhorsky, William C.
We report on the discovery and analysis of the transient X-ray pulsar CXOU J073709.1+653544 detected in the 2004 August-October Chandra and XMM-Newton observations of the nearby spiral galaxy NGC 2403. The X-ray source exhibits X-ray pulsations with a period P~18 s and a nearly sinusoidal pulse shape and pulsed fraction 46%-70% during the first th…