Search Publications
Ram Pressure Stripping of an Isolated Local Group Dwarf Galaxy: Evidence for an Intragroup Medium
McConnachie, Alan W.; Venn, Kim A.; Young, Lisa M. +2 more
We compare the stellar structure of the isolated, Local Group dwarf galaxy Pegasus (DDO 216) with low-resolution H I maps from L. M. Young et al. Our comparison reveals that Pegasus displays the characteristic morphology of ram pressure stripping; in particular, the H I has a ``cometary'' appearance that is not reflected in the regular, elliptical…
Vector Spectropolarimetry of Dark-cored Penumbral Filaments with Hinode
Lites, B. W.; Ichimoto, K.; Bellot Rubio, L. R. +9 more
We present spectropolarimetric measurements of dark-cored penumbral filaments taken with Hinode at a resolution of 0.3". Our observations demonstrate that dark-cored filaments are more prominent in polarized light than in continuum intensity. Far from disk center, the Stokes profiles emerging from these structures are very asymmetric and show evid…
Two SMC Symbiotic Stars Undergoing Steady Hydrogen Burning
Zezas, A.; Munari, U.; Orio, M. +2 more
Two symbiotic stars in the Small Magellanic Cloud (SMC), Lin 358 and SMC 3, have been supersoft X-ray sources (SSSs) for more than 10 years. We fit atmospheric and nebular models to their X-ray, optical, and UV spectra obtained at different epochs. The X-ray spectra are extremely soft and appear to be emitted by the white dwarf atmosphere, not by …
Forward Modeling of Hot Loop Oscillations Observed by SUMER and SXT
Erdélyi, R.; Wang, T. J.; Bradshaw, S. J. +1 more
An example of hot active region loop oscillations observed by SUMER and SXT is presented. The hypothesis that a fundamental mode standing slow sausage (acoustic) wave is initiated by a footpoint microflare is tested and confirmed using a forward modeling approach. The oscillation is set up immediately after the heating pulse. The duration, tempora…
Hubble Space Telescope Space Telescope Imaging Spectrograph Spectroscopy of the Environment in the Starburst Core of M82
O'Connell, R. W.; Smith, L. J.; Gallagher, J. S., III +3 more
We present optical HST STIS observations made with two slits crossing four of the optically brightest starburst clumps near the nucleus of M82. These provide Hα kinematics, extinction, electron density, and emission measures. From the radial velocity curves derived from both slits we confirm the presence of a stellar bar. We derive a new model for…
Dynamics of the Narrow-Line Region in the Seyfert 2 Galaxy NGC 1068
Kraemer, S. B.; Crenshaw, D. M.; Das, V.
We present dynamical models based on a study of high-resolution long-slit spectra of the narrow-line region (NLR) in NGC 1068 obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST). The dynamical models consider the radiative force due to the active galactic nucleus (AGN), gravitational forces from th…
Chandra and Hubble Space Telescope Observations of Gamma-Ray Blazars: Comparing Jet Emission at Small and Large Scales
Maraschi, L.; Wolter, A.; Cheung, C. C. +3 more
We present new Chandra and HST data for four gamma-ray blazars selected on the basis of radio morphology with the aim of revealing X-ray and optical emission from their jets at large scales. All the sources have been detected. Spectral energy distributions (SEDs) of the large-scale jets are obtained as well as new X-ray spectra for the blazar core…
GRO J1655-40: Early Stages of the 2005 Outburst
Smith, D. A.; Shrader, C. R.; Rupen, M. +4 more
The black hole X-ray binary transient GRO J1655-40 underwent an outburst beginning in early 2005. We present the results of our multiwavelength observational campaign to study the early outburst spectral and temporal evolution, which combines data from X-ray (RXTE and INTEGRAL), radio (VLA), and optical (ROTSE and SMARTS) instruments. During the r…
Progressive Star Formation in the Young SMC Cluster NGC 602
Tosi, M.; Sabbi, E.; Nota, A. +9 more
NGC 602 is a young stellar cluster located in a peripheral region of the Small Magellanic Cloud (SMC) known as the wing. Far from the main body of the galaxy and abutting the Magellanic Bridge, the SMC's wing is characterized by low gas and stellar content. With deep optical imaging from the Advanced Camera for Surveys (ACS) aboard the Hubble Spac…
21 cm Synthesis Observations of VIRGOHI 21-A Possible Dark Galaxy in the Virgo Cluster
Impey, Chris; van Driel, Wim; Davies, Jonathan +10 more
Many observations indicate that dark matter dominates the extragalactic universe, yet no totally dark structure of galactic proportions has ever been convincingly identified. Previously, we have suggested that VIRGOHI 21, a 21 cm source we found in the Virgo Cluster using Jodrell Bank, was a possible dark galaxy because of its broad line width (~2…