Search Publications
Probing the Evolution of the Galaxy Interaction/Merger Rate Using Collisional Ring Galaxies
Charmandaris, Vassilis; Lavery, Russell J.; Remijan, Anthony +2 more
We present the results from our program to determine the evolution of the galaxy interaction/merger rate with redshift using the unique star-forming characteristics of collisional ring galaxies. We have identified 25 distant collisional ring galaxy candidates (CRGCs) in a total of 162 deep Hubble Space Telescope (HST) Wide Field Planetary Camera 2…
Terminal Velocities of Luminous, Early-Type Stars in the Small Magellanic Cloud
Lennon, D. J.; Evans, C. J.; Heap, S. R. +2 more
Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are used to determine terminal velocities for 11 O and B-type giants and supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV resonance lines. Using archival data from observations with the Goddard High-Resolution Spectrograph and the International Ultravio…
On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions
Rubin, Robert H.; Haas, Michael R.; Colgan, Sean W. J. +2 more
Although variations in elemental abundance ratios in the Milky Way certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in…
INTEGRAL and XMM-Newton Spectral Studies of NGC 4388
Gehrels, N.; Petrucci, P. -O.; Walter, R. +4 more
We present INTEGRAL and XMM-Newton observations of a Seyfert galaxy, the type 2 active galactic nucleus (AGN) NGC 4388. Several INTEGRAL observations performed in 2003 allow us to study the spectrum in the 20-300 keV range. In addition, two XMM-Newton observations give detailed insight into the 0.2-10 keV emission. The measurements presented here …
On the Relationship between the Rotational Velocity and the Field Strength of Solar Magnetic Elements
Zhao, Junwei; Kosovichev, Alexander G.; Duvall, Thomas L., Jr.
By tracking various solar surface tracers, previous studies have found that magnetic structures, such as plages and sunspots, rotate faster than the quiet solar regions. We investigate how the rotational speed of these magnetic features is related to their magnetic field strength. By use of near-surface horizontal velocities inferred from time-dis…
Hubble Space Telescope Advanced Camera for Surveys Imaging of ω Centauri: Optical Counterpart for the Quiescent Low-Mass X-Ray Binary
Anderson, Jay; Heinke, Craig O.; Bailyn, Charles D. +5 more
We report the discovery of an optical counterpart to a quiescent neutron star in the globular cluster ω Centauri (NGC 5139). The star was found as part of our wide-field imaging study of ω Cen using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. Its magnitude and color (R625=25.2, B435-R625=1.…
The Visible and Near-Infrared Dust Opacity Law in the HH 30 Circumstellar Disk
Stapelfeldt, Karl R.; Watson, Alan M.
We present new images of the scattered-light disk around HH 30 at 0.44 and 0.81 µm. We model these images and an existing 2.04 µm image by using a multiple-scattering code, varying and fitting for the disk parameters and the dust opacity ratios at these wavelengths. A wide range of different disk geometries provide adequate fits to the…
Observations of A4059 with Chandra, Hubble Space Telescope, and the Very Large Array: Unraveling a Complex Cluster/Radio Galaxy Interaction
Perlman, Eric S.; Reynolds, Christopher S.; Heinz, Sebastian +3 more
We present a detailed reanalysis of Chandra data for the galaxy cluster A4059 and its central radio galaxy, PKS 2354-35. We also present new 1.4 and 4.7 GHz CnB-array radio data from the Very Large Array, as well as a short archival WFPC2 image from the Hubble Space Telescope. The presence of a strong interaction between this radio galaxy and the …
Characterizing the Stellar Population in NGC 1705-1
Martin, Crystal L.; Heckman, Timothy M.; Meurer, Gerhardt R. +4 more
We observed the brightest super-star cluster NGC 1705-1 in the nearby dwarf galaxy NGC 1705 with the Space Telescope Imaging Spectrograph in the echelle mode between 1200 and 3100 Å. The data allow a study of the young stellar population at hitherto unprecedented spectral resolution and signal-to-noise ratios. A comprehensive list of strong and we…
A Comparison of CME-Associated Atmospheric Waves Observed in Coronal (Fe XII 195 Å) and Chromospheric (He I 10830 Å) Lines
Gilbert, Holly R.; Thompson, Barbara J.; Holzer, Thomas E. +1 more
Although ``Moreton'' waves have historically been observed in Hα data, more recently waves have also been observed in chromospheric He I λ10830 images obtained at the Mauna Loa Solar Observatory. In an effort to better understand the nature of chromospheric waves and their relationship to coronal waves observed in EUV Imaging Telescope (EIT) data,…