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Dynamical mass estimates for two luminous star clusters in galactic merger remnants
Saglia, R. P.; Bastian, N.; Zoccali, M. +4 more
We present high-dispersion spectra of two extremely massive star clusters in galactic merger remnants, obtained using the UVES spectrograph mounted on the ESO Very Large Telescope. One cluster, W30, is located in the ~500 Myr old merger remnant NGC 7252 and has a velocity dispersion and effective radius of σ=27.5±2.5 km s-1 and Ref…
HST/STIS optical spectroscopy of five super star clusters in the starburst galaxy M82
O'Connell, R. W.; Gallagher, J. S.; Smith, L. J. +3 more
We present optical spectroscopy obtained with the Space Telescope Imaging Spectrograph of five young massive star clusters in the starburst galaxy M82. A detailed analysis is performed for one cluster `M82-A1' and its immediate environment in the starburst core. From Hubble Space Telescope archive images, we find that it is elliptical with an effe…
Penetrating the Deep Cover of Compton-thick Active Galactic Nuclei
Krolik, J. H.; Heckman, T. M.; Levenson, N. A. +2 more
We analyze observations obtained with the Chandra X-Ray Observatory of bright Compton-thick active galactic nuclei (AGNs), those with column densities in excess of 1.5×1024 cm-2 along the lines of sight. We therefore view the powerful central engines only indirectly, even at X-ray energies. Using high spatial resolution and c…
Swift Panchromatic Observations of the Bright Gamma-Ray Burst GRB 050525a
Sakamoto, T.; Campana, S.; Tagliaferri, G. +62 more
The bright gamma-ray burst GRB 050525a has been detected with the Swift observatory, providing unique multiwavelength coverage from the very earliest phases of the burst. The X-ray and optical/UV afterglow decay light curves both exhibit a steeper slope ~0.15 days after the burst, indicative of a jet break. This jet break time combined with the to…
Coronal mass ejections and magnetic flux buildup in the heliosphere
Owens, M. J.; Crooker, N. U.
To test for magnetic flux buildup in the heliosphere from coronal mass ejections (CMEs), we simulate heliospheric flux as a constant background open flux with a time-varying interplanetary CME (ICME) contribution. As flux carried by ejecta can only contribute to the heliospheric flux budget while it remains closed, the ICME flux opening rate is an…
Diapir-induced reorientation of Saturn's moon Enceladus
Nimmo, Francis; Pappalardo, Robert T.
Enceladus is a small icy satellite of Saturn. Its south polar region consists of young, tectonically deformed terrain and has an anomalously high heat flux. This heat flux is probably due to localized tidal dissipation within either the ice shell or the underlying silicate core. The surface deformation is plausibly due to upwelling of low-density …
Updating reionization scenarios after recent data
Ferrara, A.; Choudhury, T. Roy
The recent release of data on (i) high-redshift source counts from the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Hubble Ultra Deep Field (HUDF) and (ii) electron scattering optical depth from the Wilkinson Microwave Anisotropy Probe (WMAP) requires a re-examination of reionization scenarios. Using an improved self-consistent reio…
The Host Galaxies of Narrow-Line Seyfert 1 Galaxies: Nuclear Dust Morphology and Starburst Rings
Kraemer, S. B.; Crenshaw, D. M.; Deo, R. P.
We present a study of the nuclear morphology of a sample of narrow- and broad-line Seyfert 1 galaxies (NLS1s and BLS1s, respectively) based on broadband images in the Hubble Space Telescope archives. In our previous study we found that large-scale stellar bars at >1 kpc from the nucleus are more common in NLS1s than BLS1s. In this paper we find…
Hubble Space Telescope ACS Wide-Field Photometry of the Sombrero Galaxy Globular Cluster System
Spitler, Lee R.; Forbes, Duncan A.; Brodie, Jean P. +3 more
A detailed imaging analysis of the globular cluster (GC) system of the Sombrero galaxy (NGC 4594) has been accomplished using a six-image mosaic from the Hubble Space Telescope Advanced Camera for Surveys. The quality of the data is such that contamination by foreground stars and background galaxies is negligible for all but the faintest 5% of the…
Discovery of an 86 AU Radius Debris Ring around HD 181327
Henning, Thomas; Schneider, Glenn; Hines, Dean C. +11 more
HST NICMOS PSF-subtracted coronagraphic observations of HD 181327 have revealed the presence of a ringlike disk of circumstellar debris seen in 1.1 µm light scattered by the disk grains, surrounded by a diffuse outer region of lower surface brightness. The annular disk appears to be inclined by 31.7d+/-1.6d from face-on, with the disk major-…