Search Publications
Stellar Populations of Late-Type Bulges at z ≃ 1 in the Hubble Ultra Deep Field
Hathi, N. P.; Malhotra, S.; Rhoads, J. E. +5 more
We combine the exceptional depth of the Hubble Ultra Deep Field (HUDF) images and the deep GRism Advanced Camera for Surveys Program for Extragalactic Science (GRAPES) grism spectroscopy to explore the stellar populations of 34 bulges belonging to late-type galaxies at 0.8 <= z <= 1.3. The sample is selected based on the presence of a notice…
Identifications of Five INTEGRAL Sources via Optical Spectroscopy
Kaaret, Philip; Kalemci, Emrah; Walter, Roland +6 more
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is discovering hundreds of new hard X-ray sources, many of which remain unidentified. We report on optical spectroscopy of five such sources for which X-ray observations at lower energies (~0.5-10 keV) and higher angular resolutions than INTEGRAL have allowed for unique optical counter…
Compact Star Clusters in the M31 Disk
Narbutis, D.; Vansevičius, V.; Kodaira, K. +4 more
We have carried out a survey of compact star clusters (apparent size lsim3'') in the southwest part of the M31 galaxy, based on the high-resolution Suprime-Cam images (17farcm5 × 28farcm5), covering ~15% of the deprojected galaxy disk area. The UBVRI photometry of 285 cluster candidates (V lsim 20.5 mag) was performed using frames of the Local Gro…
Suzaku Wide Band Analysis of the X-Ray Variability of TeV Blazar Mrk 421 in 2006
Takahashi, Tadayuki; Tanaka, Takaaki; Kataoka, Jun +9 more
We present the results of X-ray observations of the well studied TeV blazar Mrk 421 with the Suzaku satellite in 2006 April 28. During the observation, Mrk 421 was undergoing a large flare and the X-ray flux was variable, decreasing by ~50%, from 7.8 × 10-10 to 3.7 × 10-10 erg s-1 cm-2 in about 6 hr, fol…
Reconstructing the Local Twist of Coronal Magnetic Fields and the Three-Dimensional Shape of the Field Lines from Coronal Loops in Extreme-Ultraviolet and X-Ray Images
Longcope, D. W.; Malanushenko, A.; McKenzie, D. E.
Nonlinear force-free fields are the most general case of force-free fields, but the hardest to model as well. There are numerous methods of computing such fields by extrapolating vector magnetograms from the photosphere, but very few attempts have so far made quantitative use of coronal morphology. We present a method to make such quantitative use…
Hubble Space Telescope Monitoring Reveals a 6.1 Day Period for an Ultraluminous X-Ray Source in NGC 1313
Bregman, Joel N.; McClintock, Jeffrey E.; Liu, Jifeng
Ultraluminous X-ray sources (ULXs) in nearby galaxies have X-ray luminosities of 1039-1041 erg s-1, and are possibly intermediate mass black holes of 102-105 M sun. NGC 1313 X-2 is an extreme ULX with a maximum luminosity of 3 × 1040 erg s-1, and a frequent tar…
High Resolution 36 GHz Imaging of the Supernova Remnant of SN 1987A
Gaensler, B. M.; Manchester, R. N.; Ng, C. -Y. +6 more
The aftermath of supernova (SN) 1987A continues to provide spectacular insights into the interaction between an SN blastwave and its circumstellar environment. We here present 36 GHz observations from the Australia Telescope Compact Array of the radio remnant of SN 1987A. These new images, taken in 2008 April and 2008 October, substantially extend…
The Evolution of the Scatter of the Cosmic Average Color-Magnitude Relation: Demonstrating Consistency with the Ongoing Formation of Elliptical Galaxies
Bell, Eric F.; Barden, Marco; McIntosh, Daniel H. +3 more
We present first measurements of the evolution of the scatter of the cosmic average early-type galaxy color-magnitude relation (CMR) from z = 1 to the present day, finding that it is consistent with models in which galaxies are constantly being added to the red sequence through truncation of star formation in blue cloud galaxies. We used a sample …
Stereoscopic Polar Plume Reconstructions from STEREO/SECCHI Images
Solanki, S. K.; Plunkett, S. P.; Feng, L. +7 more
We present stereoscopic reconstructions of the location and inclination of polar plumes of two data sets based on the two simultaneously recorded images taken by the EUVI telescopes in the SECCHI instrument package onboard the Solar TErrestrial RElations Observatory spacecraft. The 10 plumes investigated show a superradial expansion in the coronal…
Texes Observations of M Supergiants: Dynamics and Thermodynamics of Wind Acceleration
Harper, Graham M.; Brown, Alexander; Ryde, Nils +4 more
We have detected [Fe II] 17.94 µm and 24.52 µm emission from a sample of M supergiants (µ Cep, α Sco, α Ori, CE Tau, AD Per, and α Her) using the Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility. These low opacity emission lines are resolved at R sime 50, 000 and provide new diagnostics of the dynami…