Search Publications
The X-Ray Concentration-Virial Mass Relation
Humphrey, Philip J.; Buote, David A.; Brighenti, Fabrizio +4 more
We present the concentration (c)-virial mass (M) relation of 39 galaxy systems ranging in mass from individual early-type galaxies up to the most massive galaxy clusters, (0.06-20)×1014 Msolar. We selected for analysis the most relaxed systems possessing the highest quality data currently available in the Chandra and XMM-Newt…
Beaming Binaries: A New Observational Category of Photometric Binary Stars
Mazeh, Tsevi; Zucker, Shay; Alexander, Tal
The new photometric spaceborne survey missions COROT and Kepler will be able to detect minute flux variations in binary stars due to relativistic beaming caused by the line-of-sight motion of their components. In all but very short period binaries (P>10 days), these variations will dominate over the ellipsoidal and reflection periodic variabili…
The Physical Nature of Rest-UV Galaxy Morphology during the Peak Epoch of Galaxy Formation
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +5 more
Motivated by the irregular and little-understood morphologies of z~2-3 galaxies, we use nonparametric coefficients to quantify the morphologies of 216 galaxies that have been spectroscopically confirmed to lie at redshifts z=1.8-3.4 in the GOODS-N field. Using measurements of UV and optical spectral lines, multiband photometric data, and stellar p…
The Morphological Content of 10 EDisCS Clusters at 0.5 < z < 0.8
Pelló, R.; Poggianti, B.; Milvang-Jensen, B. +12 more
We describe Hubble Space Telescope (HST) imaging of 10 of the 20 ESO Distant Cluster Survey (EDisCS) fields. Each ~40 arcmin2 field was imaged in the F814W filter with the Advanced Camera for Surveys Wide Field Camera. Based on these data, we present visual morphological classifications for the ~920 sources per field that are brighter t…
I Zw 18 Revisited with HST ACS and Cepheids: New Distance and Age
Saha, A.; Tosi, M.; Clementini, G. +9 more
We present new V- and I-band HST ACS photometry of I Zw 18, the most metal-poor blue compact dwarf (BCD) galaxy in the nearby universe. It has been argued in the past that I Zw 18 is a very young system that started forming stars only <~500 Myr ago, but other work has hinted that older (>~1 Gyr) red giant branch (RGB) stars may also exist. O…
Exoplanet HD 209458b: Inflated Hydrogen Atmosphere but No Sign of Evaporation
Ben-Jaffel, Lotfi
Many extrasolar planets orbit closely to their parent star. Their existence raises the fundamental problem of loss and gain in their mass. For exoplanet HD 209458b, reports on an unusually extended hydrogen corona and a hot layer in the lower atmosphere seem to support the scenario of atmospheric inflation by the strong stellar irradiation. Howeve…
Survey of Magnetic Helicity Injection in Regions Producing X-Class Flares
Georgoulis, M. K.; Rust, D. M.; LaBonte, B. J.
Virtually all X-class flares produce a coronal mass ejection (CME), and each CME carries magnetic helicity into the heliosphere. Using magnetograms from the Michelson Doppler Imager on the Solar and Heliospheric Observatory, we surveyed magnetic helicity injection into 48 X-flare-producing active regions recorded by the MDI between 1996 July and 2…
Direct Measurement of the Ratio of Carbon Monoxide to Molecular Hydrogen in the Diffuse Interstellar Medium
France, Kevin; Burgh, Eric B.; McCandliss, Stephan R.
We have used archival far-ultraviolet spectra from observations made by HST STIS and FUSE to determine the column densities and rotational excitation temperatures for carbon monoxide and molecular hydrogen, respectively, along 23 sight lines to Galactic O and B stars. The reddening values range from E(B-V)=0.07 to 0.62, sampling the diffuse to tra…
The Signature of Primordial Grain Growth in the Polarized Light of the AU Microscopii Debris Disk
Matthews, Brenda C.; Graham, James R.; Kalas, Paul G.
We have used the Hubble Space Telescope Advanced Camera for Surveys coronagraph to make the first polarization maps of the AU Microscopii debris disk. The polarization rises from 5% at 20 AU to 40% at 80 AU. The polarization is perpendicular to the disk, indicating that the scattered light originates from micron-sized grains in an optically thin d…
X-Ray Absorption from the Milky Way Halo and the Local Group
Bregman, Joel N.; Lloyd-Davies, Edward J.
Million degree gas is present at near-zero redshift and is due to either a gaseous Galactic halo or a more diffuse but very massive Local Group medium. We can discriminate between these models because the column densities should depend on location in the sky, either relative to the Galaxy bulge or to the M31-Milky Way axis. To search for these sig…