Search Publications
Using Weak-Lensing Dilution to Improve Measurements of the Luminous and Dark Matter in A1689
Broadhurst, Tom; Kong, Xu; Coe, Dan +6 more
The E/S0 sequence of a cluster defines a boundary redward of which a reliable weak-lensing signal can be obtained from background galaxies, uncontaminated by cluster members. For bluer colors, both background and cluster members are present, reducing the average distortion signal by the proportion of unlensed cluster members. In deep Subaru and HS…
Spectacular Shells in the Host Galaxy of the QSO MC2 1635+119
Schweizer, François; Lacy, Mark; Stockton, Alan +4 more
We present deep HST ACS images and Keck spectroscopy of MC2 1635+119, a QSO hosted by a galaxy previously classified as an undisturbed elliptical galaxy. Our new images reveal dramatic shell structure indicative of a merger event in the relatively recent past. The brightest shells in the central regions of the host are distributed alternately in r…
Kink-induced Catastrophe in a Coronal Eruption
Liu, Rui; Alexander, David; Gilbert, Holly R.
We investigate the kinking motion and its role in the eruption of a filament/cavity system that occurred on 2002 October 31. The evolution of the eruptive filament consists of four distinct phases. After an initial slow upward acceleration, the filament experiences a quasi-static phase exhibiting kinking motions of the filament axis. The kinking p…
The Blue Straggler Population of the Globular Cluster M5
Dalessandro, E.; Beccari, G.; Ferraro, F. R. +5 more
By combining high-resolution HST and wide-field ground-based observations, in ultraviolet and optical bands, we study the blue straggler star (BSS) population of the galactic globular cluster M5 (NGC 5904) from its very central regions up to its periphery. The BSS distribution is highly peaked in the cluster center, decreases at intermediate radii…
Discovery of the Narrow-Line Seyfert 1 Galaxy Markarian 335 in a Historical Low X-Ray Flux State
Gallo, Luigi C.; Grupe, Dirk; Komossa, Stefanie
We report the discovery of the narrow-line Seyfert 1 galaxy Mrk 335 in an extremely low X-ray state. A comparison of Swift observations obtained in 2007 May and June/July with all previous X-ray observations between 1971 and 2006 show the AGN to have diminished in flux by a factor of more than 30, the lowest X-ray flux Mrk 335 has ever been observ…
On the Evolution of Coronal Mass Ejections in the Interplanetary Medium
Webb, D. F.; Fry, C. D.; Howard, T. A. +1 more
Two coronal mass ejections (CMEs) are presented which were tracked through the LASCO field of view (FOV) within 30 Rsolar and later as interplanetary CMEs (ICMEs) through the SMEI FOV from 80 to 150 Rsolar. They were also associated with erupting filaments observed by EIT, providing information on trajectory of propagation. T…
The Eruption from a Sigmoidal Solar Active Region on 2005 May 13
Liu, Chang; Wang, Haimin; Yurchyshyn, Vasyl +4 more
This paper presents a multiwavelength study of the M8.0 flare and its associated fast halo CME that originated from a bipolar NOAA AR 10759 on 2005 May 13. The source active region has a conspicuous sigmoid structure at the TRACE 171 Å channel as well as in the SXI soft X-ray images, and we mainly concern ourselves with the detailed process of the…
The Spitzer Survey of the Small Magellanic Cloud: Discovery of Embedded Protostars in the H II Region NGC 346
Stanimirović, Snežana; Bolatto, Alberto D.; Simon, Joshua D. +6 more
We use Spitzer Space Telescope observations from the Spitzer Survey of the Small Magellanic Cloud (S3MC) to study the young stellar content of N66, the largest and brightest H II region in the SMC. In addition to large numbers of normal stars, we detect a significant population of bright, red infrared sources that we identify as likely …
Metallicity and Ionization in High-Velocity Cloud Complex C
Shull, J. Michael; Giroux, Mark L.; Collins, Joseph A.
We analyze HST and FUSE ultraviolet spectroscopic data for 11 sight lines passing through the infalling high-velocity cloud (HVC) Complex C. These sight lines pass through regions with H I column densities in the range NHI=1018.1-1020.1 cm-2. From [O I/H I] abundances, we find that Complex C metallicitie…
The Leo Elliptical NGC 3379: A Metal-Poor Halo Emerges
Layden, Andrew C.; Harris, William E.; Wehner, Elizabeth M. H. +1 more
We have used the ACS camera on HST to obtain (V, I) photometry for 5300 red giant stars in the halo of the dominant Leo group member NGC 3379, a galaxy usually regarded as a classic normal giant elliptical. We use this data to derive the metallicity distribution function (MDF) for its outer-halo field stars at a location centered 33 kpc from the g…