Search Publications
Probing the Faint End of the Quasar Luminosity Function at z~ 4 in the COSMOS Field
Murayama, T.; Taniguchi, Y.; Silverman, J. D. +16 more
We searched for quasars that are ~3 mag fainter than the SDSS quasars in the redshift range 3.7 <~ z <~ 4.7 in the COSMOS field to constrain the faint end of the quasar luminosity function (QLF). Using optical photometric data, we selected 31 quasar candidates with 22 < i' < 24 at z ~ 4. We obtained optical spectra for most of these ca…
Ultra-compact Dwarfs in the Coma Cluster
Peng, Eric W.; Chiboucas, Kristin; Tully, R. Brent +6 more
We have undertaken a spectroscopic search for ultra-compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within th…
Mud volcanoes in the geologic record of Mars: The case of Firsoff crater
van Gasselt, S.; Rossi, A. P.; Pondrelli, M. +3 more
We report the detection of mound-like landforms interpreted as mud volcanoes within Firsoff crater, in the Arabia Terra region of Mars. The mounds stratigraphically overlie layered deposits within the crater, which consist of high albedo well-bedded deposits disrupted in meter-sized polygons. Hundreds of mounds are observed on the crater floor, as…
Jet Deflection by Very Weak Guide Fields during Magnetic Reconnection
Goldman, M. V.; Newman, D. L.; Lapenta, G. +2 more
Previous 2D simulations of reconnection using a standard model of initially antiparallel magnetic fields have detected electron jets outflowing from the x point into the ion outflow exhausts. Associated with these jets are extended “outer electron diffusion regions.” New PIC simulations with an ion to electron mass ratio as large as 1836 (an H
Markarian 6: Shocking the Environment of an Intermediate Seyfert
Hardcastle, M. J.; Croston, J. H.; Kraft, R. P. +4 more
Markarian 6 is a nearby (D ~ 78 Mpc) Seyfert 1.5, early-type galaxy, with a double set of radio bubbles. The outer set spans ~7.5 kpc and is expanding into the halo regions of the host galaxy. We present an analysis of our new Chandra observation, together with archival XMM-Newton data, to look for evidence of emission from shocked gas around the …
Areas of enhanced ionization in the deep nightside ionosphere of Mars
Gurnett, D. A.; Němec, F.; Morgan, D. D. +1 more
We present observations of areas of enhanced ionization located in the deep nightside ionosphere of Mars as observed by Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board the Mars Express spacecraft. Oblique ionospheric echoes coming from the same region observed during several consecutive MARSIS measurements enable us t…
A near-infrared morphological comparison of high-redshift submillimetre and radio galaxies: massive star-forming discs versus relaxed spheroids
Almaini, Omar; Dunlop, James S.; McLure, Ross J. +3 more
We present deep, high-quality K-band images of complete subsamples of powerful radio and submillimetre galaxies at redshifts z≃ 2. The data were obtained in the very best available seeing via queue-based observations at the United Kingdom Infrared Telescope and Gemini-North, with integration times scaled to ensure that comparable rest-frame surfac…
The Progenitor Mass of SN 2011dh from Stellar Population Analysis
Dolphin, Andrew E.; Dalcanton, Julianne J.; Murphy, Jeremiah W. +2 more
Using Hubble Space Telescope photometry, we characterize the age of the stellar association in the vicinity of supernova (SN) 2011dh and use it to infer the zero-age main-sequence mass (M ZAMS) of the progenitor star. We find two distinct and significant star formation (SF) events with ages of <6 and 17+3 - 4 My…
X-ray spectral evolution in the ultraluminous X-ray source M33 X-8
Middleton, Matthew J.; Sutton, Andrew D.; Roberts, Timothy P.
The bright ultraluminous X-ray source (ULX), M33 X-8, has been observed several times by XMM-Newton, providing us with a rare opportunity to 'flux bin' the spectral data and search for changes in the average X-ray spectrum with flux level. The aggregated X-ray spectra appear unlike standard sub-Eddington accretion state spectra which, alongside th…
The effect of environment on star forming galaxies at redshift. I. First insight from PACS
Berta, S.; Magnelli, B.; Nordon, R. +33 more
We use deep 70, 100 and 160 µm observations taken with PACS, the Photodetector Array Camera and Spectrometer on board of Herschel, as part of the PACS Evolutionary Probe (PEP) guaranteed time, to study the relation between star formation rate and environment at redshift ~ 1 in the GOODS-S and GOODS-N fields. We use the SDSS spectroscopic cat…