Search Publications
On the He II Emission in η Carinae and the Origin of Its Spectroscopic Events
Davidson, K.; Hillier, D. J.; Humphreys, Roberta M. +2 more
We describe and analyze Hubble Space Telescope (HST) observations of transient emission near 4680 Å in η Car, reported earlier by Steiner & Damineli. If, as seems probable, this is He II λ4687, then it is a unique clue to η Car's 5.5 yr cycle. According to our analysis, several aspects of this feature support a mass-ejection model of the obser…
Trends in the Globular Cluster Luminosity Function of Early-Type Galaxies
Jordán, Andrés; Tonry, John L.; Côté, Patrick +8 more
We present results from a study of the globular cluster luminosity function (GCLF) in a sample of 89 early-type galaxies observed as part of the ACS Virgo Cluster Survey. Using a Gaussian parameterization of the GCLF, we find a highly significant correlation between the GCLF dispersion, σ, and the galaxy luminosity, MB,gal, in the sense…
Spitzer IRAC Images and Sample Spectra of Cassiopeia A's Explosion
Smith, J. D.; Reach, William T.; Rho, Jeonghee +5 more
We present Spitzer IRAC images and representative 5.27-38.5 µm IRS spectra of the Cas A SNR. We find that various IRAC channels are each most sensitive to a different spectral and physical component. Channel 1 (3.6 µm) provides an excellent match to the radio synchrotron images. Where channel 1 is strong with respect to the other IRAC …
Stochastic Acceleration in the Galactic Center HESS Source
Melia, Fulvio; Liu, Siming; Petrosian, Vahé +1 more
Stochastic acceleration of electrons interacting resonantly with a turbulent magnetic field in a small accretion torus appears to be the likely mechanism responsible for much of Sagittarius A*'s millimeter and shorter wavelength spectrum. The longer wavelength radiation is produced at larger radii by electrons either diffusing from smaller scales …
Central Star Formation and PAH Profiles in Pseudobulges and Classical Bulges
Fisher, David B.
I use Spitzer 3.6-8.0 µm color profiles and surface brightness profiles of polycyclic aromatic hydrocarbons (PAHs) to compare the radial structure of star formation in pseudobulges and classical bulges. Pseudobulges are ``bulges'' that form through secular evolution, rather than mergers. In this study, pseudobulges are identified using the p…
A Near-Infrared Analysis of the Submillimeter Background and the Cosmic Star-Formation History
Wang, W. -H.; Barger, A. J.; Cowie, L. L.
We use new deep NIR and MIR observations to analyze the 850 µm image of the GOODS-N region. We show that much of the submillimeter background is picked out by sources with H(AB) or 3.6 µm(AB)<23.25 (1.8 µJy). These sources contribute an 850 µm background of 24+/-2 Jy deg-2. This is a much higher fraction of th…
XMM-Newton Observations of the Supernova Remnant IC 443. I. Soft X-Ray Emission from Shocked Interstellar Medium
Troja, E.; Bocchino, F.; Reale, F.
The shocked interstellar medium around IC 443 produces strong X-ray emission in the soft energy band (E<~1.5 keV). We present an analysis of such emission as observed with the EPIC MOS cameras on board the XMM-Newton observatory, with the purpose to find clear signatures of the interactions with the interstellar medium (ISM) in the X-ray band, …
The AGN Outflow in the HDF-S Target QSO J2233-606 from a High-Resolution VLT UVES Spectrum
Arav, Nahum; Kim, Tae-Sun; Gabel, Jack R.
We present a detailed analysis of the intrinsic UV absorption in the central HDF-S target QSO J2233-606, based on a high-resolution, high-S/N (~25-50) spectrum obtained with VLT UVES. This spectrum samples the cluster of intrinsic absorption systems outflowing from the AGN at radial velocities v~-5000 to -3800 km s-1 in the key far-UV d…
An Investigation into the Variability of Heating in a Solar Active Region
Winebarger, Amy R.; Warren, Harry P.; Ugarte-Urra, Ignacio
Previous studies have indicated that both steady and impulsive heating mechanisms play a role in active region heating. In this paper, we present a study of 20 hours of soft X-ray and EUV observations of solar active region NOAA AR 8731. We examine the evolution of six representative loop structures that brighten and fade first from X-ray images a…
The Evolution of the Mass Function Split by Morphology up to Redshift 1 in the FORS Deep and the GOODS-S Fields
Pannella, M.; Salvato, M.; Saglia, R. P. +5 more
We study the evolution of the stellar mass density for the separate families of bulge-dominated and disk-dominated galaxies over the redshift range 0.25<=z<=1.15. We derive quantitative morphology for a statistically significant galaxy sample of 1645 objects selected from the FORS Deep Field and the GOODS-S field. We find that the morphologi…