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The Hot Stars of Old Open Clusters: M67, NGC 188, and NGC 6791
O'Connell, Robert W.; Bohlin, Ralph C.; Landsman, Wayne +4 more
We analyze ultraviolet (~1500 Å) images of the old open clusters M67, NGC 188, and NGC 6791 obtained with the Ultraviolet Imaging Telescope (UIT) during the second flight of the Astro observatory in 1995 March. Twenty stars are detected on the UIT image of M67, including 11 blue stragglers, seven white dwarf candidates, and the yellow giant-white …
The Infrared Morphology of eta Carinae
Smith, Nathan; Gehrz, Robert D.; Krautter, Joachim
We present results of a recent 2-12 µm ground-based infrared (IR) imaging study of Eta Carinae. We discuss the comparative spatial morphology of the bipolar lobes, the ``skirt'' defined by the equatorial ejecta, and the bright features in the core. We derive separate color temperature values of 200, 240, and 420 K for the bipolar lobes, skir…
On the Use of [Na/Fe] and [alpha/Fe] Ratios and Hipparcos-based (U, V, W) Velocities as Age Indicators among Low-Metallicity Halo Field Giants
Sneden, Christopher; Hanson, Robert B.; Kraft, Robert P. +1 more
We have examined the [Na/Fe] and [Mg/Fe] ratios in a sample of 68 field halo giants with -3 <~ [Fe/H] <~ -1. We recalculated the Galactic (U, V, W) velocity components for these stars, using Hipparcos proper motions and a new Hipparcos-based distance scale. We used these data to see how the abundance ratios may relate to kinematical substruc…
A Study of Nine High-Redshift Clusters of Galaxies. I. The Survey
Postman, Marc; Lubin, Lori M.; Oke, J. B.
We present a description of the observations and data reduction procedures for an extensive spectroscopic and multiband photometric study of nine high-redshift, optically selected cluster candidates. The primary goal of the survey is to establish new constraints on cluster and galaxy evolution, with specific emphasis on the evolution of galaxy mor…
Ultraviolet Imaging Telescope Observations of the Magellanic Clouds
Parker, Joel Wm.; O'Connell, Robert W.; Bohlin, Ralph C. +8 more
We present wide-field far-ultraviolet (FUV; 1300-1800 Å) images of the Large and Small Magellanic Clouds (LMC, SMC). These data were obtained by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 (1990 December 1-10) and Astro-2 (1995 March 2-18) missions; the images provide an extensive FUV mosaic of the SMC and contain numerous regions i…
A Three-mode, Variable Velocity Jet Model for HH 34
Noriega-Crespo, A.; Raga, A.
Variable ejection velocity jet models can qualitatively explain the appearance of successive working surfaces in Herbig-Haro (HH) jets. This paper presents an attempt to explore which features of the HH 34 jet can indeed be reproduced by such a model. From previously published data on this object, we find evidence for the existence of a three-mode…
Infrared Observations of Ongoing Star Formation in the 30 Doradus Nebula and a Comparison with Hubble Space Telescope WFPC 2 Images
Walborn, Nolan R.; Barbá, Rodolfo H.; Rubio, Mónica +3 more
Intercomparisons of ground-based IR continuum and H_2 images with Hubble Space Telescope WFPC2 images of the 30 Dor Nebula reveal detailed structural relationships, which provide new information about current star formation there. Numerous stellar IR sources have been discovered in or near the bright nebular filaments west and northeast of R136; t…
A Cluster of Low-Redshift LYalpha Clouds toward PKS 2155-304. I. Limits on Metals and D/H
Carilli, Chris; Shull, J. Michael; Stocke, John T. +4 more
We report observations from the Hubble Space Telescope (HST) and the VLA on the galactic environment, metallicity, and D/H in strong low-redshift Lyalpha absorption systems toward the bright BL Lac object PKS 2155-304. These studies are intended to clarify the origin and chemical evolution of gas at large distances from galaxies. With GHRS/G160M d…
Wide Field Planetary Camera 2 Observations of the Brown Dwarf Gliese 229B: Optical Colors and Orbital Motion
Kulkarni, S. R.; Golimowski, D. A.; Burrows, C. J. +2 more
Three-epoch observations of the M1 V-plus-brown dwarf system Gliese 229AB using the Hubble Space Telescope's Wide Field Planetary Camera 2 (WFPC2) are reported. Relative astrometric measurements spanning 1 year confirm the common proper motion of the pair and reveal the first evidence of orbital motion. The radial and azimuthal components of Gl 22…
Nonparametric Reconstruction of Abell 2218 from Combined Weak and Strong Lensing
Saha, Prasenjit; Williams, Liliya L. R.; Abdelsalam, Hanadi M.
We apply a new nonparametric technique to reconstruct, with uncertainties, the projected mass distribution of the inner region of Abell 2218 using combined strong and weak lensing constraints from multiple-image systems and arclets with known redshifts. The reconstructed mass map broadly resembles previous, less detailed parametric models, but whe…