Search Publications
On the Origin of Ultraviolet Emission and the Accretion Model of Low-luminosity Active Galactic Nuclei
Ho, Luis C.; Yuan, Feng; Yu, Zhaolong
Low-luminosity active galactic nuclei (LLAGNs) are generally believed to be powered by an inner radiatively inefficient, advection-dominated accretion flow (ADAF), an outer truncated thin disk, and a jet. Maoz recently challenged this picture based on the observation that the strength of ultraviolet emission relative to the X-ray and radio bands d…
The Resolved Stellar Halo of NGC 253
Bell, Eric F.; Radburn-Smith, David J.; Bailin, Jeremy +2 more
We have obtained Magellan/IMACS and Hubble Space Telescope (HST)/Advanced Camera for Surveys imaging data that resolve red giant branch stars in the stellar halo of the starburst galaxy NGC 253. The HST data cover a small area, and allow us to accurately interpret the ground-based data, which cover 30% of the halo to a distance of 30 kpc, allowing…
The ACS Fornax Cluster Survey. X. Color Gradients of Globular Cluster Systems in Early-type Galaxies
Jordán, Andrés; Liu, Chengze; Côté, Patrick +4 more
We use the largest homogeneous sample of globular clusters (GCs), drawn from the ACS Virgo Cluster Survey (ACSVCS) and ACS Fornax Cluster Survey (ACSFCS), to investigate the color gradients of GC systems in 76 early-type galaxies. We find that most GC systems possess an obvious negative gradient in (g-z) color with radius (bluer outward), which is…
Discovery of Cold, Pristine Gas Possibly Accreting onto an Overdensity of Star-forming Galaxies at Redshift z ~ 1.6
Dickinson, Mark; Ferguson, Henry C.; Giavalisco, Mauro +11 more
We report the discovery of large amounts of cold (T ~ 104 K), chemically young gas in an overdensity of galaxies at redshift z ≈ 1.6 located in the Great Observatories Origins Deep Survey southern field. The gas is identified thanks to the ultra-strong Mg II λ2800 absorption features it imprints onto the rest-frame UV spectra of galaxie…
The Megaparsec-scale X-ray Jet of The BL Lac Object OJ287
Jorstad, Svetlana G.; Marscher, Alan P.
We present an X-ray image of the BL Lacertae (BL Lac) object OJ287 revealing a long jet, curved by 55° and extending 20'' or 90 kpc from the nucleus. This de-projects to >1 Mpc based on the viewing angle on parsec scales. Radio emission follows the general X-ray morphology but extends even farther from the nucleus. The upper limit to the isotro…
A Multiphase Absorber Containing O VI and Broad H I Directly Tracing 106 K Plasma at Low Redshift Toward HE 0153-4520
Savage, B. D.; Narayanan, A.; Wakker, B. P. +1 more
Observations of the QSO HE 0153-4520 (z em = 0.450) with the Cosmic Origins Spectrograph (COS) from 1134 to 1796 Å with a resolution of ~17 km s-1 and a signal-to-noise ratio per resolution element of 20-40 are used to study a multiphase partial Lyman limit system (LLS) at z = 0.22601 tracing both cool and hot gas. Far-Ultrav…
Molecular Gas in Lensed z >2 Quasar Host Galaxies and the Star Formation Law for Galaxies with Luminous Active Galactic Nuclei
Riechers, Dominik A.
We report the detection of luminous CO(J = 2→1), CO(J = 3→2), and CO(J = 4→3) emission in the strongly lensed high-redshift quasars B1938+666 (z = 2.059), HE 0230-2130 (z = 2.166), HE 1104-1805 (z = 2.322), and B1359+154 (z = 3.240), using the Combined Array for Research in Millimeter-wave Astronomy. B1938+666 was identified in a "blind" CO redshi…
Star Formation from DLA Gas in the Outskirts of Lyman Break Galaxies at z ~ 3
Rafelski, Marc; Chen, Hsiao-Wen; Wolfe, Arthur M.
We present evidence for spatially extended low surface brightness emission around Lyman break galaxies (LBGs) in the V-band image of the Hubble Ultra Deep Field, corresponding to the z ~ 3 rest-frame far-UV (FUV) light, which is a sensitive measure of star formation rates (SFRs). We find that the covering fraction of molecular gas at z ~ 3 is not …
Discovery of an Ultrasoft X-Ray Transient Source in the 2XMM Catalog: A Tidal Disruption Event Candidate
Lin, Dacheng; Grupe, Dirk; Carrasco, Eleazar R. +3 more
We have discovered an ultrasoft X-ray transient source, 2XMMi J184725.1-631724, which was detected serendipitously in two XMM-Newton observations in the direction of the center of the galaxy IC 4765-f01-1504 at a redshift of 0.0353. These two observations were separated by 211 days, with the 0.2-10 keV absorbed flux increasing by a factor of about…
Spectroscopy of Luminous z > 7 Galaxy Candidates and Sources of Contamination in z > 7 Galaxy Searches
Kneib, J. -P.; Aussel, H.; Sanders, D. B. +22 more
We present three bright z +-dropout candidates selected from deep near-infrared (NIR) imaging of the COSMOS 2 deg2 field. All three objects match the 0.8-8 µm colors of other published z > 7 candidates but are 3 mag brighter, facilitating further study. Deep spectroscopy of two of the candidates covering 0.64-1.02 &m…