Search Publications
Meeting the Cool Neighbors. X. Ultracool Dwarfs from the 2MASS All-Sky Data Release
Kirkpatrick, J. Davy; Reid, I. Neill; Lowrance, Patrick +5 more
Using data from the 2 Micron All Sky Survey All-Sky Point Source Catalogue, we have extended our census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitude of 15°. Starting with an initial catalog of 2,139,484 sources, we have winnowed the sample to 467 candidate late-type M or L dwarfs within 20 pc of the Sun. Fi…
The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei
Maiolino, Roberto; Brandt, W. N.; Kaspi, Shai +2 more
We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3-3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/LEdd) and the hard X-ray photon index (Γ) for 35 moderate- to high-lum…
The EPIC-MOS particle-induced background spectra
Kuntz, K. D.; Snowden, S. L.
Context: To analyze diffuse emission that fills the field of view, one must accurately characterize the instrumental backgrounds. For the XMM-Newton EPIC-MOS instrument these backgrounds include a temporally variable “quiescent” component, as well as the strongly variable soft proton contamination.
Aims: We have characterized the spectral and …
Origin of Coronal Shock Waves. Invited Review
Vršnak, Bojan; Cliver, Edward W.
The basic idea of the paper is to present transparently and confront two different views on the origin of large-scale coronal shock waves, one favoring coronal mass ejections (CMEs), and the other one preferring flares. For this purpose, we first review the empirical aspects of the relationship between CMEs, flares, and shocks (as manifested by ra…
The Radial Velocity Experiment (RAVE): Second Data Release
Gilmore, G.; Freeman, K. C.; Evans, N. W. +51 more
We present the second data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity, and rotational velocity) of up to one million stars using the 6 dF multi-object spectrograph on the 1.2 m UK Schmidt Telescope of t…
The structures of distant galaxies - I. Galaxy structures and the merger rate to z ~ 3 in the Hubble Ultra-Deep Field
Conselice, Christopher J.; Rajgor, Sheena; Myers, Robert
This paper begins a series in which we examine the structures of distant galaxies to directly determine the history of their formation modes. We start this series by examining the structures of zF850LP < 27 galaxies in the Hubble Ultra-Deep Field (UDF), the deepest high-resolution optical image taken to date. We investigate a few bas…
Inverse Compton Origin of the Hard X-Ray and Soft Gamma-Ray Emission from the Galactic Ridge
Bouchet, L.; Porter, Troy A.; Strong, Andrew W. +2 more
A recent redetermination of the nonthermal component of the hard X-ray to soft γ-ray emission from the Galactic ridge, using the SPI instrument on the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), is shown to be well reproduced as inverse Compton emission from the interstellar medium. Both cosmic-ray primary electrons and secondary e…
The Nucleus of the Sagittarius Dsph Galaxy and M54: a Window on the Process of Galaxy Nucleation
Dalessandro, E.; Bellazzini, M.; Monaco, L. +6 more
We present the results of a thorough study of the nucleus of the Sgr dwarf spheroidal galaxy (Sgr dSph) and of the bright globular cluster M54 (NGC 6715) that resides within the same nucleus (Sgr,N). We have obtained accurate radial velocities and metallicity estimates for 1152 candidate red giant branch stars of Sgr and M54 lying within ~9' from …
Hydrocarbon lakes on Titan: Distribution and interaction with a porous regolith
Callahan, P.; Gim, Y.; Stofan, E. +11 more
Synthetic Aperture Radar (SAR) images of Titan's north polar region reveal quasi-circular to complex features which are interpreted to be liquid hydrocarbon lakes. We investigate methane transport in Titan's hydrologic cycle using the global distribution of lake features. As of May 2007, the SAR data set covers ~22% of the surface and indicates mu…
A Highly Complete Spectroscopic Survey of the GOODS-N Field
Wang, W. -H.; Barger, A. J.; Cowie, L. L.
We present a table of redshifts for 2907 galaxies and stars in the 145 arcmin2 HST ACS GOODS-North, making this the most spectroscopically complete redshift sample obtained to date in a field of this size. We also include the redshifts, where available, in a table containing just under 7000 galaxies from the ACS area with Ks, AB