Search Publications
Narrowband HST Images of M87: Evidence for a Disk of Ionized Gas around a Massive Black Hole
Kriss, Gerard A.; Bohlin, Ralph C.; Hartig, George F. +7 more
We present HST WFPC2 narrowband Hα + [N II] images of M87 which show a small disk of ionized gas with apparent spiral structure surrounding the nucleus of M87. The jet projects ~19.5^deg^ from the minor axis of the disk, which suggests that the jet is approximately normal to the disk. In a companion Letter, Harms et al. measure radial velocities a…
The Abundant Elements in Interstellar Dust
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A.
We explore the incorporation of the cosmically abundant species O, C, N, Mg, Si, Fe, and S into interstellar dust. Column densities based on Goddard High Resolution Spectrograph 3.5 km/s resolution measurements from the literature for eight individual absorbing regions toward five lines of sight are used. Corrections are applied as needed in order…
HST Photometry of the Trapezium Cluster
Stauffer, John R.; Prosser, Charles F.; Hartmann, Lee +4 more
We have obtained images of 11 fields in the Trapezium cluster with the Planetary Camera (PC) of the Hubble Space Telescope (HST) in order to extend Herbig & Terndrup's (1986) study of this prototype, dense embedded cluster to fainter magnitudes than is possible from the ground. Using these images, we have identified 319 stars within an area of…
Multiwavelength Tests of the Dusty Torus Model for Seyfert Galaxies
Mulchaey, John S.; Wilson, Andrew S.; Kinney, Anne L. +5 more
We present a compilation of emission properties for a sample of 116 Seyfert galaxies based on both previously unpublished data and measurements available in the literature. These measurements include fluxes in the emission lines [O III] λ5007 and Hβ, as well as the infrared (25-60 microns), ultraviolet (1450 A), soft (0.2-4 keV), and hard (2-10 ke…
Morphological Studies of the Galaxy Populations in Distant ``Butcher-Oemler'' Clusters with HST. I. AC 114 at Z = 0.31 and Abell 370 at Z = 0.37
Smail, Ian; Ellis, Richard S.; Sharples, Ray M. +1 more
We present the first results of an ongoing program we are undertaking with the Wide Field Camera of the Hubble Space Telescope (HST) to understand the physical origin of the enhanced star formation seen in moderate-redshift (z ~ 0.3-0.4) cluster galaxies. Deep HST exposures have been obtained for the central regions of two rich compact "Butcher- O…
Hubble Space Telescope Imaging of Super--Star Clusters in NGC 1569 and NGC 1705
O'Connell, Robert W.; Gallagher, John S., III; Hunter, Deidre A.
We examine the structural properties of three super-star clusters in the nearby, H I-rich galaxies NGC 1569 and NGC 1705. The clusters, which have total absolute V magnitudes between - 13.3 and - 14.1, appear to be point sources on ground-based images but are partially resolved in new images obtained with the Hubble Space Telescope (HST) Planetary…
The Morphology of Distant Cluster Galaxies. I. HST Observations of CL 0939+4713
Dressler, Alan; Oemler, Augustus, Jr.; Butcher, Harvey R. +1 more
We have obtained Hubble Space Telescope (HST) WFC observations of CL 0939+4713, a very rich cluster at z = 0.41 which exhibits an excess population of blue galaxies typical of clusters at that redshift. The images are of sufficient quality, despite the HST spherical aberration problems, to permit assignment of Hubble types to galaxies brighter tha…
An IUE Survey of Interstellar H i Lyman-Alpha Absorption. II. Interpretations
Savage, Blair D.; Diplas, Athanassios
We present an analysis of interstellar neutral hydrogen column densities obtained from archival Ly alpha absorption line data toward the complete sample of B2 and hotter stars observed at high spectral resolution with the IUE satellite. The full sample includes 554 stars and more than doubles the number of lines of sight previously observed. Many …
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. V. Variability of the Ultraviolet Continuum and Emission Lines of NGC 3783
Altieri, B.; Mazeh, T.; Shull, J. M. +61 more
We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variabili…
The Balmer-dominated Northeast Limb of the Cygnus Loop Supernova Remnant
Blair, William P.; Raymond, John C.; Hester, J. Jeff
We present a comprehensive investigation of the Balmar-dominated northeast limb of the Cygnus Loop supernova remnant. Data presented include H alpha (O III), and X-ray images, UV and visible spectrophotometry, and high-resolution spectroscopy. The two relatively bright Balmer-dominated filaments visible on the POSS prints are seen to be part of a …