Search Publications
The Evolutionary History of Galactic Bulges: Photometric and Spectroscopic Studies of Distant Spheroids in the GOODS Fields
Treu, Tommaso; Ellis, Richard S.; MacArthur, Lauren A. +3 more
We report on the first results of a new study aimed at understanding the diversity and evolutionary history of distant galactic bulges in the context of now well-established trends for pure spheroidal galaxies. To this end, bulges have been isolated for a sample of 137 spiral galaxies within the redshift range 0.1 < z < 1.2 in the GOODS fiel…
Emerging Active Regions Studied with Ring-Diagram Analysis
Howe, R.; Komm, R.; Hill, F. +1 more
We study the temporal variation of subsurface flows associated with emerging active regions, focusing on four regions in detail. Two of them, AR 10314 and AR 10488, emerge near disk center and the other two, AR 10365 and AR 10375, are older regions where new flux emerges during their disk passage. We measure the horizontal subsurface flows from hi…
Chandra X-Ray Observatory Observations of the Globular Cluster M71
Ransom, Scott M.; Weisskopf, Martin C.; Bogdanov, Slavko +12 more
We observe the nearby, low-density globular cluster M71 (NGC 6838) with the Chandra X-Ray Observatory to study its faint X-ray populations. Five X-ray sources are found inside the cluster core radius, including the known eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light curve of the source coincident with this MSP shows ma…
On the Magnetic Structure of the Solar Transition Region
Judge, Philip; Centeno, Rebecca
We examine the hypothesis that cool loops dominate emission from solar transition region plasma below temperatures of 2 × 105 K. We compare published VAULT images of H Lyα, a lower transition region line, with nearly contemporaneous magnetograms from Kitt Peak, obtained during the second flight (VAULT-2) on 2002 June 14. The measured su…
Very Large Array Observations of Galactic Center OH 1720 MHz Masers in Sagittarius A East and in the Circumnuclear Disk
Sjouwerman, Loránt O.; Pihlström, Ylva M.
We present Very Large Array (VLA) radio interferometry observations of the 1720 MHz OH masers in the Galactic center (GC). Most 1720 MHz OH masers arise in regions where the supernova remnant Sgr A East is interacting with the interstellar medium. The majority of the newly found 1720 MHz OH masers are located to the northeast, independently indica…
A Search for New Galactic Magnetars in Archival Chandra and XMM-Newton Observations
Miller, J. M.; Muno, M. P.; Gaensler, B. M. +2 more
We present constraints on the number of Galactic magnetars, which we have established by searching for sources with periodic variability in 506 archival Chandra observations and 441 archival XMM-Newton observations of the Galactic plane (| b| < 5°). Our search revealed four sources with periodic variability on timescales of 200-5000 s, all of w…
Non-Gaussian Line Profiles in a Large Solar Flare Observed on 2006 December 13
Mariska, J. T.; Hara, H.; Watanabe, T. +4 more
We have studied the characteristics of the non-Gaussian line profile of the Fe XIV 274.20 Å line in and around a flare arcade. We found that broad non-Gaussian line profiles associated with redshifts are observed in the flare arcade. There were two typical types of broad line profiles. One was a distorted line profile caused by multiple flows, and…
A Statistical Study of Solar Active Regions That Produce Extremely Fast Coronal Mass Ejections
Wang, Yuming; Zhang, Jie
We present statistical results on the properties of the solar source regions that produced the 57 fastest (>=1500 km s-1) front-side coronal mass ejections (CMEs) from 1996 June to 2007 January. The properties of these fast-CME-producing regions, 35 in total, are compared with those of all 1143 active regions (ARs) in the period stud…
Toward a Robust Estimate of the Merger Rate Evolution Using Near-IR Photometry
Hammer, Francois; Kembhavi, Ajit K.; Rawat, A. +1 more
We use a combination of deep, high angular resolution imaging data from the CDFS (HST/ACS GOODS survey) and ground-based near-IR Ks images to derive the evolution of the galaxy major merger rate in the redshift range 0.2 <= z<= 1.2. We select galaxies solely on the basis of their J-band rest-frame absolute magnitude, which is a go…
Reappraising Transition Region Line Widths in Light of Recent Alfvén Wave Discoveries
De Pontieu, Bart; McIntosh, Scott W.; Tarbell, Theodore D.
We provide a new interpretation of ultraviolet transition region emission line widths observed by the SUMER instrument on the Solar and Heliospheric Observatory (SOHO). This investigation is prompted by observations of the chromosphere at unprecedented spatial and temporal resolution from the Solar Optical Telescope (SOT) on Hinode revealing that …