Search Publications
The Stellar Masses and Star Formation Histories of Galaxies at z ~ 6: Constraints from Spitzer Observations in the Great Observatories Origins Deep Survey
Dickinson, Mark; Ferguson, Henry C.; Giavalisco, Mauro +3 more
Using the deep Spitzer Infrared Array Camera (IRAC) observations of the Great Observatories Origins Deep Survey (GOODS), we study the stellar masses and star formation histories of galaxies at z~6 based on the i775-band dropout sample selected from the GOODS fields. In total, we derive stellar masses for 53 i775-band dropouts…
The XMM-Newton/Chandra monitoring campaign of the Galactic center region. Description of the program and preliminary results
Wijnands, R.; Homan, J.; van der Klis, M. +10 more
We present the first results of our X-ray monitoring campaign on a 1.7 square degree region centered on Sgr A* using the satellites XMM-Newton and Chandra. The purpose of this campaign is to monitor the behavior (below 10 keV) of X-ray sources (both persistent and transient) which are too faint to be detected by monitoring instruments aboard other…
The Chandra view of the 3C/FR I sample of low luminosity radio-galaxies
Capetti, A.; Grandi, P.; Balmaverde, B.
We present results from Chandra observations of the 3C/FR I sample of low luminosity radio-galaxies. We detected a power-law nuclear component in 12 objects out of the 18 with available data. In 4 galaxies we detected nuclear X-ray absorption at a level of NH ∼ (0.2{-}6) × 1022 cm-2. X-ray absorbed sources are asso…
A Prominent Accretion Disk in the Low-Hard State of the Black Hole Candidate SWIFT J1753.5-0127
Miller, J. M.; Homan, J.; Miniutti, G.
We report on simultaneous XMM-Newton and RXTE observations of the stellar mass black hole candidate SWIFT J1753.5-0127. The source was observed in the ``low-hard'' state, during the decline of a hard outburst. The inner accretion disk is commonly assumed to be radially truncated in the low-hard state, and it has been suggested that this property m…
The Depiction of Coronal Structure in White-Light Images
Morgan, Huw; Habbal, Shadia Rifai; Woo, Richard
The very steep decrease in density with heliocentric distance makes imaging of coronal density structures out to a few solar radii challenging. The radial gradient in brightness can be reduced using numerous image processing techniques, thus quantitative data are manipulated to provide qualitative images. We introduce a new normalizing-radial-grad…
XMM-Newton Archival Study of the Ultraluminous X-Ray Population in Nearby Galaxies
Reynolds, Christopher S.; Mushotzky, Richard F.; Winter, Lisa M.
We present the results of an archival XMM-Newton study of the bright X-ray point sources (LX>1038 ergs s-1) in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state counterpart to the ultraluminous X-ray (ULX) population, searching for a soft-hard s…
Chemical Compositions of Red Giant Stars in Old Large Magellanic Cloud Globular Clusters
Stetson, Peter B.; Johnson, Jennifer A.; Ivans, Inese I.
We have observed 10 red giant stars in four old Large Magellanic Cloud globular clusters with the high-resolution spectrograph MIKE on the Magellan Landon Clay 6.5 m telescope. The stars in our sample have up to 20 elemental abundance determinations for the α-, iron peak, and neutron-capture element groups. We have also derived abundances for the …
Stabilization of the disk around βPictoris by extremely carbon-rich gas
Weinberger, Alycia J.; Roberge, Aki; Feldman, Paul D. +2 more
The edge-on disk surrounding the nearby young star βPictoris is the archetype of `debris disks', which are composed of dust and gas produced by collisions between-and evaporation of-planetesimals, analogues of Solar System comets and asteroids. These disks may provide insight into the formation and early evolution of terrestrial planets. Previous …
Clusters at Half Hubble Time: Galaxy Structure and Colors in RX J0152.7-1357 and MS 1054-03
Ford, H. C.; Demarco, R.; Tran, Kim-Vy H. +12 more
We study the photometric and structural properties of spectroscopically confirmed members in the two massive X-ray-selected z~0.83 galaxy clusters MS 1054-03 and RX J0152.7-1357 using three-band mosaic imaging with the Hubble Space Telescope Advanced Camera for Surveys. The samples include 105 and 140 members of RX J0152.7-1357 and MS 1054-03, res…
RHESSI and SOHO CDS Observations of Explosive Chromospheric Evaporation
Milligan, Ryan O.; Gallagher, Peter T.; Mathioudakis, Mihalis +3 more
Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory. For the first time, cospatial imaging and spectroscopy have been used to observe explosive ev…