Search Publications
Superresolving Distant Galaxies with Gravitational Telescopes: Keck Laser Guide Star Adaptive Optics and Hubble Space Telescope Imaging of the Lens System SDSS J0737+3216
Treu, Tommaso; Gavazzi, Raphaël; Marshall, Philip J. +13 more
We combine high-resolution images in four optical/infrared bands, obtained with the laser guide star adaptive optics (LGSAO) system on the Keck telescope and with the Hubble Space Telescope (HST), to study the gravitational lens system SDSS J0737+3216 (lens redshift 0.3223, source redshift 0.5812). We show that (under favorable observing condition…
A Keck Spectroscopic Survey of MS 1054-03 (z = 0.83): Forming the Red Sequence
Franx, Marijn; Kelson, Daniel D.; Illingworth, Garth D. +4 more
Using a magnitude-limited, spectroscopic survey of the X-ray-luminous galaxy cluster MS 1054-03, we isolate 153 cluster galaxies and measure MS 1054's redshift and velocity dispersion to be z=0.8307+/-0.0004 and σz=1156+/-82 km s-1. The absorption-line, poststarburst (``E+A''), and emission-line galaxies, respectively, make u…
Shock Heating in the Nearby Radio Galaxy NGC 3801
Hardcastle, M. J.; Croston, J. H.; Kraft, R. P.
We report the Chandra detection of shock-heated shells of hot gas surrounding the radio lobes of the nearby (DL~53 Mpc) low-power radio galaxy NGC 3801. The shells have temperatures of 1 and 0.7 keV, compared to an ISM temperature of 0.23 keV. The estimated expansion speed of the shells is ~850 km s-1, corresponding to a Mach…
The Solar Eclipse of 2006 and the Origin of Raylike Features in the White-Light Corona
Koutchmy, S.; Sheeley, N. R., Jr.; Wang, Y. -M. +3 more
Solar eclipse observations have long suggested that the white-light corona is permeated by long fine rays. By comparing photographs of the 2006 March 29 total eclipse with current-free extrapolations of photospheric field measurements and with images from the Solar and Heliospheric Observatory (SOHO), we deduce that the bulk of these linear featur…
The Mass Assembly History of Spheroidal Galaxies: Did Newly Formed Systems Arise via Major Mergers?
Treu, Tommaso; Ellis, Richard S.; Bundy, Kevin
We examine the properties of a morphologically selected sample of 0.4<z<1.0 spheroidal galaxies in the GOODS fields in order to ascertain whether or not their increase in abundance with time arises primarily from major mergers. To address this question, we determine the scaling relations between the dynamical mass Mdyn, determined…
The AU Microscopii Debris Disk: Multiwavelength Imaging and Modeling
Duchêne, Gaspard; Fitzgerald, Michael P.; Graham, James R. +2 more
Debris disks around main-sequence stars are produced by the destruction of unseen parent bodies. AU Microscopii (GJ 803) is a compelling object to study in the context of disk evolution across different spectral types, as it is an M dwarf whose nearly edge-on disk may be directly compared to that of its A5 V sibling β Pic. We resolve the disk from…
Evolution of Dust and Ice Features around FU Orionis Objects
Quanz, S. P.; Henning, Th.; van Boekel, R. +5 more
We present spectra for a sample of 14 FUors and two T Tauri stars observed with Spitzer or ISO. Based on the appearance of the 10 µm silicate feature, we define two categories of FUors. Objects showing the silicate feature in absorption (Category 1) are still embedded in a circumstellar envelope. The shape of the silicate bands is in good ag…
``Bursty'' Reconnection Following Solar Eruptions: MHD Simulations and Comparison with Observations
Lin, Jun; Riley, Pete; Mikić, Zoran +4 more
Posteruptive arcades are frequently seen in the aftermath of coronal mass ejections (CMEs). The formation of these loops at successively higher altitudes, coupled with the classic ``two-ribbon'' flare seen in Hα, are interpreted as reconnection of the coronal magnetic field that has been dragged outward by the CME. White-light observations of ``ra…
VLA and XMM-Newton Observations of the SNR W41/TeV Gamma-Ray Source HESS J1834-087
Wang, Q. D.; Leahy, D. A.; Li, Z. +1 more
The recently discovered extended TeV source HESS J1834-087 is associated with both a diffuse X-ray enhancement and a molecular cloud, projected at the center of an old radio supernova remnant, G23.3-0.3 (SNR W41). New H I observations from the VLA Galactic Plane Survey (VGPS) show unambiguous structures associated with W41 in the radial velocity r…
Why Do Some Intermediate Polars Show Soft X-Ray Emission? A Survey of XMM-Newton Spectra
Hellier, Coel; Evans, P. A.
We make a systematic analysis of the XMM-Newton X-ray spectra of intermediate polars (IPs) and find that, contrary to the traditional picture, most show a soft blackbody component. We compare the results with those from AM Her stars and deduce that the blackbody emission arises from reprocessing of hard X-rays, rather than from the blobby accretio…