Search Publications
Coronal Plasma Motions near Footpoints of Active Region Loops Revealed from Spectroscopic Observations with Hinode EIS
Harra, Louise K.; Doschek, George A.; Hara, Hirohisa +4 more
The solar active region 10938 has been observed from the disk center to the west limb with the Hinode EUV Imaging Spectrometer. In the disk-center observation, subsonic upflow motions of tens of km s-1 and enhanced nonthermal velocities have been found near the footpoints of the active region loops assuming a single Gaussian approximati…
Emergence of a Helical Flux Rope under an Active Region Prominence
Shibata, Kazunari; Tsuneta, Saku; Shimizu, Toshifumi +12 more
Continuous observations were obtained of NOAA AR 10953 with the Solar Optical Telescope (SOT) on board the Hinode satellite from 2007 April 28 to May 9. A prominence was located over the polarity inversion line (PIL) to the southeast of the main sunspot. These observations provided us with a time series of vector magnetic fields on the photosphere…
Cosmic Evolution of Black Holes and Spheroids. III. The MBH-σ* Relation in the Last Six Billion Years
Treu, Tommaso; Malkan, Matthew A.; Blandford, Roger D. +1 more
We measure the evolution of the correlation between black hole mass and host spheroid velocity dispersion (MBH-σ*) over the last 6 billion years, by studying three carefully selected samples of active galaxies at z = 0.57, z = 0.36 and z < 0.1. For all three samples, virial black hole masses are consistently estimated usin…
The Evolution of AGN Host Galaxies: From Blue to Red and the Influence of Large-Scale Structures
Popesso, P.; Lehmer, B. D.; Alexander, D. M. +14 more
We present an analysis of 109 moderate-luminosity (41.9 <= log L0.5-8.0 keV <= 43.7) AGNs in the Extended Chandra Deep Field-South survey, which is drawn from 5549 galaxies from the COMBO-17 and GEMS surveys having 0.4 <= z<= 1.1. These obscured or optically weak AGNs facilitate the study of their host galaxies since the AGN…
Reconciling the Metallicity Distributions of Gamma-Ray Burst, Damped Lyα, and Lyman Break Galaxies at z ≈ 3
Prochaska, J. Xavier; Fynbo, Johan P. U.; Dessauges-Zavadsky, Miroslava +2 more
We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyα (DLA) systems are drawn from the population of UV-selected star-forming, high-z galaxies (generally referred to as Lyman break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations …
Comparing and Calibrating Black Hole Mass Estimators for Distant Active Galactic Nuclei
Treu, Tommaso; Malkan, Matthew A.; Woo, Jong-Hak +1 more
Black hole mass (MBH) is a fundamental property of active galactic nuclei (AGNs). In the distant universe, MBH is commonly estimated using the Mg II, Hβ, or Hα emission line widths and the optical/UV continuum or line luminosities as proxies for the characteristic velocity and size of the broad-line region. Although they all …
Relativistic Iron Emission Lines in Neutron Star Low-Mass X-Ray Binaries as Probes of Neutron Star Radii
Homan, Jeroen; Miller, Jon M.; Cackett, Edward M. +6 more
Using Suzaku observations of three neutron star low-mass X-ray binaries (Ser X-1, 4U 1820-30, and GX 349+2) we have found broad, asymmetric, relativistic Fe K emission lines in all three objects. These Fe K lines can be well fit by a model for lines from a relativistic accretion disk ("diskline"), allowing a measurement of the inner radius of the …
Flows and Nonthermal Velocities in Solar Active Regions Observed with the EUV Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?
Culhane, J. L.; Doschek, G. A.; Mariska, J. T. +4 more
From Doppler velocity maps of active regions constructed from spectra obtained by the EUV Imaging Spectrometer (EIS) on the Hinode spacecraft we observe large areas of outflow (20-50 km s-1) that can persist for at least a day. These outflows occur in areas of active regions that are faint in coronal spectral lines formed at typical qui…
Three-dimensional MHD Simulation of the 2003 October 28 Coronal Mass Ejection: Comparison with LASCO Coronagraph Observations
Vourlidas, Angelos; Lugaz, Noé; Roussev, Ilia I. +6 more
We numerically model the coronal mass ejection (CME) event of 2003 October 28 that erupted from AR 10486 and propagated to Earth in less than 20 hr, causing severe geomagnetic storms. The magnetohydrodynamic (MHD) model is formulated by first arriving at a steady state corona and solar wind employing synoptic magnetograms. We initiate two CMEs fro…
Evidence for Merger Remnants in Early-Type Host Galaxies of Low-Redshift QSOs
Schweizer, François; Lacy, Mark; Stockton, Alan +4 more
We present results from a pilot HST ACS deep imaging study in broadband V of five low-redshift QSO host galaxies classified in the literature as ellipticals. The aim of our study is to determine whether these early-type hosts formed at high redshift and have since evolved passively, or whether they have undergone relatively recent mergers that may…