Search Publications
Sunspot Rotation, Sigmoidal Filament, Flare, and Coronal Mass Ejection: The Event on 2000 February 10
Yan, X. L.; Kong, D. F.; Qu, Z. Q. +1 more
We find that a sunspot with positive polarity had an obvious counterclockwise rotation and resulted in the formation and eruption of an inverse S-shaped filament in NOAA Active Region 08858 from 2000 February 9 to 10. The sunspot had two umbrae which rotated around each other by 195° within about 24 hr. The average rotation rate was nearly 8° hr
Warm Gas in the Virgo Cluster. I. Distribution of Lyα Absorbers
Chen, Hsiao-Wen; Yoon, Joo Heon; Putman, Mary E. +2 more
The first systematic study of the warm gas (T = 104 - 5 K) distribution across a galaxy cluster is presented using multiple background QSOs in and around the Virgo Cluster. We detect 25 Lyα absorbers (NH I = 1013.1-15.4 cm-2) in the Virgo velocity range toward 9 of 12 QSO sightlines observed with the Co…
The Star Formation History of M32
Monachesi, Antonela; Lauer, Tod R.; Dressler, Alan +5 more
We use deep Hubble Space Telescope Advanced Camera for Surveys/High Resolution Channel observations of a field within M32 (F1) and an M31 background field (F2) to determine the star formation history (SFH) of M32 from its resolved stellar population. We find that 2-5 Gyr old stars contribute ~40% ± 17% of M32's mass, while ~55% ± 21% of M32's mass…
CLASH: Discovery of a Bright z ~= 6.2 Dwarf Galaxy Quadruply Lensed by MACS J0329.6-0211
Shu, X.; Zheng, W.; Molino, A. +22 more
We report the discovery of a z phot = 6.18+0.05 - 0.07 (95% confidence level) dwarf galaxy, lensed into four images by the galaxy cluster MACS J0329.6-0211 (zl = 0.45). The galaxy is observed as a high-redshift dropout in HST/ACS/WFC3 CLASH and Spitzer/IRAC imaging. Its redshift is securely determined du…
Weak-lensing Results for the Merging Cluster A1758
Bradač, M.; Markevitch, M.; Gonzalez, A. H. +2 more
Here we present the weak-lensing results for A1758, which is known to consist of four subclusters undergoing two separate mergers, A1758N and A1758S. Weak-lensing results for A1758N agree with previous weak-lensing results for clusters 1E0657-558 (Bullet cluster) and MACS J0025.4-1222, whose X-ray gas components were found to be largely separated …
Sizing up Partially Depleted Galaxy Cores
Graham, Alister W.; Dullo, Bililign T.
We have modeled the inner surface brightness profiles of 39 alleged "core" galaxies with the core-Sérsic model, and provide new physical parameters for the largest ever sample of "core" galaxies fit with this model. When present, additional nuclear components were simultaneously modeled and the typical root-mean-square scatter of the fits (out to …
Dust-to-gas Ratio in the Extremely Metal-poor Galaxy I Zw 18
Cannon, John M.; Bolatto, Alberto D.; Leroy, Adam K. +7 more
The blue compact dwarf galaxy I Zw 18 is one of the most metal-poor systems known in the local universe (12+log(O/H) = 7.17). In this work we study I Zw 18 using data from Spitzer, Herschel Space Telescope, and IRAM Plateau de Bure Interferometer. Our data set includes the most sensitive maps of I Zw 18, to date, in both the far-infrared and the C…
Dark Matter Search Using XMM-Newton Observations of Willman 1
Loewenstein, Michael; Kusenko, Alexander
We report the results of a search for an emission line from radiatively decaying dark matter in the ultra-faint dwarf spheroidal galaxy Willman 1 based on analysis of spectra extracted from XMM-Newton X-ray Observatory data. The observation follows up our analysis of Chandra data of Willman 1 that resulted in line flux upper limits over the Chandr…
The Chandra View of NGC 4178: The Lowest Mass Black Hole in a Bulgeless Disk Galaxy?
Cheung, C. C.; Böker, T.; Secrest, N. J. +3 more
Using high-resolution Chandra data, we report the presence of a weak X-ray point source coincident with the nucleus of NGC 4178, a late-type bulgeless disk galaxy known to have high-ionization mid-infrared (mid-IR) lines typically associated with active galactic nuclei (AGNs). Although the faintness of this source precludes a direct spectral analy…
Evidence for a Wide Range of Ultraviolet Obscuration in z ~ 2 Dusty Galaxies from the GOODS-Herschel Survey
Dickinson, Mark; Daddi, Emanuele; Dey, Arjun +20 more
Dusty galaxies at z ~ 2 span a wide range of relative brightness between rest-frame mid-infrared (8 µm) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios >~ 1000, might be abnormally bright in the…