Search Publications
Analysis of Spatial Structure of the Spica H II Region
Park, J. -W.; Min, K. -W.; Edelstein, J. +2 more
Far ultraviolet (FUV) spectral images of the Spica H II region are first presented here for the Si II* λ1533.4 and Al II λ1670.8 lines and then compared with the optical Hα image. The Hα and Si II* images show enhanced emissions in the southern part of the H II region where H I density increases outward. This high density region, which we identify…
Multiple Weak Deflections in Galaxy-Galaxy Lensing
Brainerd, Tereasa G.
The frequency and effects of multiple weak deflections in galaxy-galaxy lensing are investigated via Monte Carlo simulations. The lenses in the simulations are galaxies with known redshifts and known rest-frame blue luminosities. The frequency of multiple deflections above a given threshold shear value is quantified for discrete source redshifts, …
Extinction and Distance to Anomalous X-ray Pulsars from X-ray Scattering Halos
van Kerkwijk, M. H.; Rivera-Ingraham, A.
We analyze the X-ray scattering halos around three Galactic Anomalous X-ray Pulsars in order to constrain the distance and the optical extinction of each source. We obtain surface brightness distributions from EPIC-pn data obtained with XMM-Newton, compare the profiles of different sources, and fit them with a model based on the standard theory of…
The Role of Magnetic Topology in the Heating of Active Region Coronal Loops
Reeves, Katharine K.; Golub, L.; Leka, K. D. +4 more
We investigate the evolution of coronal loop emission in the context of the coronal magnetic field topology. New modeling techniques allow us to investigate the magnetic field structure and energy release in active regions (ARs). Using these models and high-resolution multi-wavelength coronal observations from the Transition Region and Coronal Exp…
Cosmic-ray Spallation in Radio-quiet Active Galactic Nuclei: A Case Study of NGC 4051
Turner, T. J.; Miller, L.
We investigate conditions for and consequences of spallation in radio-quiet Seyfert galaxies. The work is motivated by the recent discovery of significant line emission at 5.44 keV in Suzaku data from NGC 4051. The energy of the new line suggests an identification as Cr I Kα emission; however, the line is much stronger than would be expected from …
Fine Magnetic Features and Chirality in Solar Active Region NOAA 10930
Zhang, Hongqi
In this paper, we present fine magnetic features near the magnetic inversion line in the solar active region NOAA 10930. The high-resolution vector magnetograms obtained by Hinode allow detailed analyses around magnetic fibrils in the active region. The analyses are based on the fact that the electric current density can be divided into two compon…
XMM-Newton Observations of the Seyfert 2 Galaxy NGC 7590: The Nature of X-ray Absorption
Shu, X. W.; Wang, J. X.; Liu, T.
We present the analysis of three XMM-Newton observations of the Seyfert 2 galaxy NGC 7590. The source was found to have no X-ray absorption in the low spatial resolution ASCA data. The XMM-Newton observations provide a factor of ~10 better spatial resolution than previous ASCA data. We find that the X-ray emission of NGC 7590 is dominated by an of…
The Opacity of Galactic Disks at z ~ 0.7
Kneib, J. -P.; Ilbert, O.; Taniguchi, Y. +13 more
We compare the surface brightness-inclination relation for a sample of COSMOS pure disk galaxies at z ~ 0.7 with an artificially redshifted sample of Sloan Digital Sky Survey (SDSS) disks well matched to the COSMOS sample in terms of rest-frame photometry and morphology, as well as their selection and analysis. The offset between the average surfa…
Ignition Column Depths of Helium-rich Thermonuclear Bursts from 4U 1728-34
Galloway, Duncan K.; Misanovic, Zdenka; Cooper, Randall L.
We analyzed thermonuclear (type I) X-ray bursts observed from the low-mass X-ray binary 4U 1728-34 by RXTE, Chandra, and INTEGRAL. We compared the variation in burst energy and recurrence times as a function of accretion rate with the predictions of a numerical ignition model including a treatment of the heating and cooling in the crust. We found …
Growth of Massive Black Holes at Their Late Stage
Cao, Xinwu; Xu, Ya-Di
It is believed that the growth of local massive black holes was dominated by accretion during quasar phases, while a fraction of the local black hole mass was accumulated through accreting gases at very low rates. We derive the black hole mass density as a function of redshift with the bolometric luminosity function of active galactic nuclei (AGNs…