Search Publications
Comparison of White Dwarf Models with STIS Spectrophotometry
Bohlin, Ralph C.
Computed flux distributions for four white dwarf (WD) stars with nearly pure hydrogen atmospheres are tied to the Vega flux scale with V-band Landolt photometry. With broadband photometric precision in the range 0.2%-0.4%, Space Telescope Imaging Spectrograph (STIS) low-dispersion spectrophotometry tightly constrains the relative continuum fluxes …
A Search for OH Megamasers at Z > 0.1. I. Preliminary Results
Giovanelli, Riccardo; Darling, Jeremy
We present the preliminary results of a survey for OH megamasers underway at the Arecibo Observatory.1 The goals of the survey are to calibrate the luminosity function of OH megamasers to the low-redshift galaxy merger rate (0.1<z<0.2) and to use the enhanced sample of OH megamasers provided by the survey to study OH megamaser environments, …
The Evolving Morphology of the Bipolar Nebula M2-9
Corradi, R. L. M.; Balick, Bruce; Schwarz, H. E. +1 more
The planetary nebula M2-9 has drastically changed its shape since its discovery by Minkwoski. Although the outline of the nebula seems to be stationary, most of the knots and bright features (N1, N2, S1, and S2) have moved laterally from the west to the east edges of both lobes. These features and their changes have reflection, not point, symmetry…
A Distance-Independent Age for the Globular Cluster M92
Grundahl, F.; Stetson, P. B.; Andersen, M. I. +2 more
We use deep Strömgren CCD photometry to determine the age of the globular cluster M92 (NGC 6341) from the [(v-y)0,c0]-diagram. Besides being completely independent of distance, this color-color plot has the further advantage that it is not very sensitive to the amount of foreground interstellar absorption. The main disadvanta…
Wide Field Planetary Camera 2 Imaging of Young Clusters in the Magellanic Clouds
Da Costa, G. S.; Bessell, M. S.; Keller, Stefan C.
We have carried out Wide Field Planetary Camera 2 (WFPC2) F160BW, F555W, and F656N imaging of four young populous clusters: NGC 330, in the Small Magellanic Cloud, and NGC 1818, 2004, and 2100, in the Large Magellanic Cloud. We report photometric results for these four clusters, including identification using photometric colors of the cluster Be s…
A Keck Survey of Gravitational Lens Systems. I. Spectroscopy of SBS 0909+532, HST 1411+5211, and CLASS B2319+051
Blandford, R. D.; Fassnacht, C. D.; Readhead, A. C. S. +2 more
We present new results from a continuing Keck program designed to study gravitational lens systems. We have obtained redshifts for three lens systems, SBS 0909+532, HST 1411+5211, and CLASS B2319+051. For all of these systems, either the source or lens redshift (or both) has been previously unidentified. Our observations provide some of these miss…
Deep Hubble Space Telescope STIS Color-Magnitude Diagrams of the Dwarf Irregular Galaxy WLM: Detection of the Horizontal Branch
Gregg, Michael D.; Minniti, Dante; Goudfrooij, Paul +3 more
We have obtained V- and I-band photometry for 1886 stars down to I=27 and V=28 in the field of the dwarf irregular galaxy WLM, using deep Space Telescope Imaging Spectrograph (STIS) CL- and LP-band images taken in the parallel mode with the Hubble Space Telescope. The photometry is used to study the horizontal branch identified in WLM. The horizon…
The White Dwarf Cooling Age of the Open Cluster NGC 2420
Gilmore, Gerard; von Hippel, Ted
We have used deep HST WFPC2 observations of two fields in NGC 2420 to produce a cluster color-magnitude diagram down to V~27. After imposing morphological selection criteria we find eight candidate white dwarfs in NGC 2420. Our completeness estimates indicate that we have found the terminus of the WD cooling sequence. We argue that the cluster dis…
The Star Formation History of the Starburst Region NGC 2363 and its Surroundings
Drissen, Laurent; Robert, Carmelle; Doyon, René +2 more
We present Hubble Space Telescope optical images and UV spectra, as well as ground-based near-infrared images of the high surface-brightness giant H II region NGC 2363 (NGC 2366-I) and its surroundings. The massive star content of the southern end of the dwarf irregular galaxy NGC 2366 is investigated, with an emphasis on Wolf-Rayet and red superg…
A Search for Faint Companions to Nearby Stars Using the Wide Field Planetary Camera 2
Krist, John E.; Golimowski, David A.; Schroeder, Daniel J. +9 more
We have completed a direct-imaging search for faint companions (FCs) to 23 stars within 13 pc of the Sun using the Hubble Space Telescope Planetary Camera. The strategy of this search changed considerably from that reported in 1996. To maximize the image contrast between potential FCs and a target star's point-spread function, we adopted the F1042…