Search Publications
A Celestial Gamma-Ray Foreground Due to the Albedo of Small Solar System Bodies and a Remote Probe of the Interstellar Cosmic-Ray Spectrum
Porter, Troy A.; Digel, Seth W.; Moskalenko, Igor V. +2 more
We calculate the γ-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids (MBAs), Jovian and Neptunian Trojan asteroids, and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the γ-ray albedo for the Main Belt, Trojans, and Kuiper Belt strongly depends on the small-body size distrib…
Complex Organic Materials in the HR 4796A Disk?
Li, Aigen; Mann, I.; Köhler, M.
The red spectral shape of the visible to near-infrared reflectance spectrum of the sharply edged ringlike disk around the young main-sequence star HR 4796A was recently interpreted as the presence of tholin-like complex organic materials which are seen in the atmosphere and surface of Titan and the surfaces of icy bodies in the solar system. Howev…
Validation of Two MHD Models of the Solar Corona with Rotational Tomography
Sokolov, Igor V.; Hayashi, Keiji; Frazin, Richard A. +4 more
We demonstrate a validation of two 3D MHD models of the corona by comparing density values from solar rotational tomography (SRT) to densities and morphological properties of the two MHD solutions for CR 2029 (2005 April 21-May 18). The two MHD models are given by the Stanford and Michigan models, and both use the same synoptic magnetogram from MD…
Black Hole Accretion in Low-Mass Galaxies since z ~ 1
Rieke, George; Shi, Yong; Willmer, Christopher +3 more
We have selected a sample of X-ray-emitting active galactic nuclei (AGNs) in low-mass host galaxies (~5 × 109-2 × 1010 M⊙) out to z ~ 1. By comparing to AGNs in more massive hosts, we have found that the AGN spatial number density and the fraction of galaxies hosting AGNs depends strongly on the host mass, with the…
The Origin of Polar Streamers in the Solar Corona
Llebaria, A.; Zhukov, A. N.; Lamy, P. +2 more
We investigate the large-scale three-dimensional (3D) structure of the solar corona near the maximum of the 23rd solar cycle in an attempt to determine the origin of polar streamers. We use a model that allows us to simulate the quasi-stationary configuration of the large-scale coronal density distribution. The coronal neutral line, as given by th…
The Signature of Evolving Turbulence in Quiet Solar Wind as Seen by Ulysses
Chapman, S. C.; Nicol, R. M.; Dendy, R. O.
Solar wind fluctuations, such as magnetic field or velocity, show power-law power spectra suggestive both of an inertial range of intermittent turbulence (with ~-5/3 exponent), and at lower frequencies, of fluctuations of coronal origin (with ~-1 exponent). The Ulysses spacecraft spent many months in the quiet fast solar wind above the Sun's polar…
Disintegration of Magnetic Flux in Decaying Sunspots as Observed with the Hinode SOT
Kubo, M.; Lites, B. W.; Ichimoto, K. +8 more
Continuous observations of sunspot penumbrae with the Solar Optical Telescope aboard Hinode clearly show that the outer boundary of the penumbra fluctuates around its averaged position. The penumbral outer boundary moves inward when granules appear in the outer penumbra. We discover that such granules appear one after another while moving magnetic…
Understanding the Relations between QSOs and Their Host Galaxies from Combined HST Imaging and VLT Spectroscopy
Magain, P.; Courbin, F.; Hutsemékers, D. +2 more
The host galaxies of six nearby QSOs are studied on the basis of high-resolution HST optical images and spatially resolved VLT slit spectra. The gas ionization and velocity are mapped as a function of the distance to the central QSO. In the majority of the cases, the QSO significantly contributes to the gas ionization in its whole host galaxy, and…
Interstellar Krypton Abundances: The Detection of Kiloparsec-scale Differences in Galactic Nucleosynthetic History
Sofia, Ulysses J.; Meyer, David M.; Cartledge, Stefan I. B. +2 more
We present an analysis of Kr I λ1236 line measurements from 50 sight lines in the Hubble Space Telescope Space Telescope Imaging Spectrograph and Goddard High Resolution Spectrograph data archives that have sufficiently high resolution and signal-to-noise ratio to permit reliable krypton-to-hydrogen abundance ratio determinations. The distribution…
XMM-Newton Observations of Broad Absorption Line Quasars with Polar Outflows
Zhou, Hongyan; Wang, Huiyuan; Jiang, Peng +3 more
We have selected a sample of broad absorption line (BAL) quasars which show significant radio variations, indicating the presence of polar BAL outflows. We obtained snapshot XMM observations of four polar BAL QSOs, to check whether strong X-ray absorption, one of the most prominent characteristics of most BAL QSOs, also exists in polar outflows. T…