Search Publications
Weak Hard X-Ray Emission from Broad Absorption Line Quasars: Evidence for Intrinsic X-Ray Weakness
Harrison, F. A.; Stern, D.; Zhang, W. W. +19 more
We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z = 0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z < 1.3. However, their rest-frame ≈2 keV luminosities are 14 to >330 times weaker than expected for typical quasars. Our results from a p…
The Dynamical Fingerprint of Core Scouring in Massive Elliptical Galaxies
Saglia, R. P.; Thomas, J.; Bender, R. +2 more
The most massive elliptical galaxies have low-density centers or cores that differ dramatically from the high-density centers of less massive ellipticals and bulges of disk galaxies. These cores have been interpreted as the result of mergers of supermassive black hole binaries, which depopulate galaxy centers by gravitationally slingshotting centr…
Fingerprints of Galactic Loop I on the Cosmic Microwave Background
Liu, Hao; Mertsch, Philipp; Sarkar, Subir
We investigate possible imprints of galactic foreground structures such as the "radio loops" in the derived maps of the cosmic microwave background. Surprisingly, there is evidence for these not only at radio frequencies through their synchrotron radiation, but also at microwave frequencies where emission by dust dominates. This suggests the mecha…
Constraints on the Progenitor System of the Type Ia Supernova 2014J from Pre-explosion Hubble Space Telescope Imaging
Filippenko, Alexei V.; Cenko, S. Bradley; Kelly, Patrick L. +7 more
We constrain the properties of the progenitor system of the highly reddened Type Ia supernova (SN Ia) 2014J in Messier 82 (M82; d ≈ 3.5 Mpc). We determine the supernova (SN) location using Keck-II K-band adaptive optics images, and we find no evidence for flux from a progenitor system in pre-explosion near-ultraviolet through near-infrared Hubble …
Wide Cool and Ultracool Companions to Nearby Stars from Pan-STARRS 1
Chambers, Kenneth C.; Magnier, Eugene A.; Wainscoat, Richard J. +18 more
We present the discovery of 57 wide (>5'') separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS 1 (PS1) data and the spectral classification of 31 previously known companions. Our companions represent a selective subsample of promising candidates and span a range in spectral type…
Infall of Nearby Galaxies into the Virgo Cluster as Traced with Hubble Space Telescope
Dolphin, Andrew E.; Wu, Po-Feng; Shaya, Edward J. +2 more
We measured the tip of the red giant branch distances to nine galaxies in the direction to the Virgo cluster using the Advanced Camera for Surveys on the Hubble Space Telescope. These distances put seven galaxies (GR 34, UGC 7512, NGC 4517, IC 3583, NGC 4600, VCC 2037, and KDG 215) in front of Virgo and two galaxies (IC 3023 and KDG 177) likely in…
Molecular Gas in the X-Ray Bright Group NGC 5044 as Revealed by ALMA
Ohyama, Youichi; Brighenti, Fabrizio; Jones, Christine +17 more
An ALMA observation of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow, detected 24 molecular structures within the central 2.5 kpc. The masses of the molecular structures vary from 3 × 105 M ⊙ to 107 M ⊙ and the CO(2-1) linewidths vary fr…
The ACS LCID Project. X. The Star Formation History of IC 1613: Revisiting the Over-cooling Problem
Ferguson, Henry C.; Dolphin, Andrew E.; Skillman, Evan D. +13 more
We present an analysis of the star formation history (SFH) of a field near the half-light radius in the Local Group dwarf irregular galaxy IC 1613 based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. Our observations reach the oldest main sequence turn-off, allowing a time resolution at the oldest ages of ~1 Gyr. Our analysis …
Herschel Finds Evidence for Stellar Wind Particles in a Protostellar Envelope: Is This What Happened to the Young Sun?
Ceccarelli, C.; Dominik, C.; Caux, E. +4 more
There is evidence that the young Sun emitted a high flux of energetic (>=10 MeV) particles. The collisions of these particles with the material at the inner edge of the Protosolar Nebula disk induced spallation reactions that formed short-lived radionuclei, like 10Be, whose trace is now visible in some meteorites. However, it is poor…
Asymmetry in the CME-CME Interaction Process for the Events from 2011 February 14-15
Temmer, M.; Veronig, A. M.; Vršnak, B. +1 more
We present a detailed study of the interaction process of two coronal mass ejections (CMEs) successively launched on 2011 February 14 (CME1) and 2011 February 15 (CME2). Reconstructing the three-dimensional shape and evolution of the flux ropes, we verify that the two CMEs interact. The frontal structure of both CMEs, measured along different posi…