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Kinematics of the Broad-Line Region in M81
Devereux, Nick; Shearer, Andrew
A new model is presented that explains the origin of the broad emission lines observed in the LINER/Seyfert nucleus of M81 in terms of a steady state spherically symmetric inflow, amounting to ~1×10-5 Msolar yr-1, which is sufficient to explain the luminosity of the active galactic nucleus (AGN). The emitting volum…
GRB 050713A: High-Energy Observations of the Gamma-Ray Burst Prompt and Afterglow Emission
Gehrels, N.; Pagani, C.; Stamerra, A. +14 more
Swift discovered GRB 050713A and slewed promptly to begin observing with its narrow-field instruments 72.6 s after the burst onset, while the prompt gamma-ray emission was still detectable in the BAT. Simultaneous emission from two flares is detected in the BAT and XRT. This burst marks just the second time that the BAT and XRT have simultaneously…
Lensing Signals in the Hubble Ultra Deep Field Using All Second-Order Shape Deformations
Anderson, Jay; Irwin, John; Shmakova, Marina
The long exposure times of the Hubble Ultra Deep Field (UDF) together with empirically derived position-dependent point-spread functions have enabled us to measure two distinct nonlinear shape distortions of galaxies. We have previously argued that nonlinear lensing from small (109-1010 Msolar) dense objects in the…
A Search for Lyman Break Galaxies at z>8 in the NICMOS Parallel Imaging Survey
Teplitz, Harry I.; Siana, Brian; Malkan, Matthew A. +4 more
We have selected 14 J-dropout Lyman break galaxy (LBG) candidates with J110-H160>=2.5 from the NICMOS Parallel Imaging Survey. This survey consists of 135 arcmin2 of imaging in 228 independent sight lines, reaching average 5 σ sensitivities of J110=25.8 and H160=25.6 (AB). Distinguishing th…
A Catastrophic Flux Rope in a Quadrupole Magnetic Field for Coronal Mass Ejections
Wang, J. -X.; Zhang, Y. -Z.
We propose a flux-rope model for the initiation of flare-associated CMEs. The model triggers the eruption with a catastrophic loss of MHD equilibrium and then requires magnetic reconnection to sustain the eruption's acceleration. We carry out 2.5-dimensional time-dependent resistive MHD simulations, choosing the initial state such that a flux rope…
The Frequency of Mid-Infrared Excess Sources in Galactic Surveys
Indebetouw, R.; Benjamin, R. A.; Wolfire, M. G. +27 more
We have identified 230 Tycho-2 Spectral Catalog stars that exhibit 8 µm mid-IR extraphotospheric excesses in the MSX and Spitzer GLIMPSE surveys. Of these, 183 are either OB stars earlier than B8 in which the excess plausibly arises from a thermal bremsstrahlung component or evolved stars in which the excess may be explained by an atmospheri…
Circumnuclear Star Clusters in the Galaxy Merger NGC 6240, Observed with Keck Adaptive Optics and the Hubble Space Telescope
Schneider, G.; Max, C. E.; Pollack, L. K.
We discuss images of the central ~10 kpc (in projection) of the galaxy merger NGC 6240 at H and K' bands, taken with the NIRC2 narrow camera on Keck II using natural guide star adaptive optics. We detect 28 star clusters in the NIRC2 images, of which only 7 can be seen in the similar spatial resolution, archival WFPC2 Planetary Camera data at eith…
Observational Consequences of the Hypothesized Helium-rich Stellar Population in ω Centauri
Terndrup, D. M.; Newsham, G.
In response to the proposed high-helium content stars as an explanation for the double main sequence observed in ω Centauri, we investigated the consequences of such stars elsewhere on the color-magnitude diagram. We concentrated on the horizontal branch, where the effects of high helium are expected to show themselves more clearly. In the process…
Photometric Properties of the Most Massive High-Redshift Galaxies
Hernquist, Lars; Cox, Thomas J.; Hopkins, Philip F. +2 more
We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution hydrodynamical simulations of the hierarchical formation of a z~6 quasar, stellar population synthesis models, t…
The 1-200 keV X-Ray Spectrum of NGC 2992 and NGC 3081
Gehrels, N.; Beckmann, V.; Tueller, J.
The Seyfert 2 galaxies NGC 2992 and NGC 3081 have been observed by INTEGRAL and Swift. We report the results and a comparison of the spectrum above 10 keV based on INTEGRAL IBIS/ISGRI, Swift/BAT, and BeppoSAX/PDS. A spectrum can be extracted in the X-ray energy band ranging from 1 up to 200 keV. Although NGC 2992 shows a complex spectrum below 10 …