Search Publications
Stellar Populations in Three Outer Fields of the Large Magellanic Cloud
Cole, Andrew A.; Ballester, Gilda E.; Crisp, David +15 more
We present Hubble Space Telescope photometry for three fields in the outer disk of the Large Magellanic Cloud (LMC) extending approximately 4 mag below the faintest main-sequence turnoff. We cannot detect any strongly significant differences in the stellar populations of the three fields based on the morphologies of the color-magnitude diagrams, t…
Observational Properties of the Orion Nebula Proplyds
O'Dell, C. R.
Hubble Space Telescope Planetary Camera images have been used to quantitatively determine key parameters characterizing emission-line proplyds in the Orion Nebula. A previous conclusion that the objects are radiation-bounded ionization fronts is confirmed and found to be in excellent agreement with the observations. Only a very loose correlation o…
Navy Prototype Optical Interferometer Observations of the Double Stars Mizar A and Matar
Hajian, Arsen R.; Hutter, D. J.; Hummel, C. A. +3 more
We present a detailed analysis of two spectroscopic binaries based on new observations obtained with the Navy Prototype Optical Interferometer (NPOI). While the data calibration needs refinement, first results show the impressive potential of NPOI, both in terms of speed and precision, for imaging and modeling the orbits of spectroscopic binaries.…
A Radio Study of the Seyfert Galaxy IC 5063: Evidence for Fast Gas Outflow
Tsvetanov, Z.; Morganti, R.; Oosterloo, T.
We present new radio continuum (8 and 1.4 GHz) and H i 21 cm line observations of the Seyfert 2 galaxy IC 5063 (PKS 2048-572), obtained with the Australia Telescope Compact Array. The high-resolution 8 GHz image reveals a linear triple structure ~4" (1.3 kpc) in size. This small-scale radio emission shows a strong morphological association with th…
A Study of Nine High-Redshift Clusters of Galaxies. II. Photometry, Spectra, and Ages of Clusters 0023+0423 and 1604+4304
Postman, Marc; Lubin, Lori M.; Oke, J. B.
We present an extensive photometric and spectroscopic study of two high-redshift clusters of galaxies based on data obtained from the Keck 10 m telescopes and the Hubble Space Telescope. The clusters Cl 0023+0423 (z = 0.84) and Cl 1604+4304 (z = 0.90) are part of a multiwavelength program of Oke, Postman & Lubin to study nine candidate cluster…
Photometry of Proxima Centauri and Barnard's Star Using Hubble Space Telescope Fine Guidance Sensor 3: A Search for Periodic Variations
Hemenway, P. D.; Jefferys, W. H.; Nelan, E. +10 more
We have observed Proxima Centauri and Barnard's star with the Hubble Space Telescope Fine Guidance Sensor 3. Proxima Cen exhibits small-amplitude, periodic photometric variations. Once several sources of systematic photometric error are corrected, we obtain 2 mmag internal photometric precision. We identify two distinct behavior modes over the pas…
Modeling the Brightness Profiles of the Orion Proplyds
Henney, W. J.; Arthur, S. J.
We investigate whether simple models of a photoevaporated flow from an externally ionized neutral clump or wind can reproduce the observed Hα intensity profiles of the proplyds in the inner Orion Nebula. We find that models fitted to the bright ``cusp'' at the head of each proplyd successfully predict the brightness distribution of the extended di…
Keck HIRES Spectroscopy of M92 Subgiants: Surprising Abundances near the Turnoff
King, Jeremy R.; Boesgaard, Ann M.; Stephens, Alex +1 more
Using high-resolution, moderate signal-to-noise ratio spectroscopy obtained with the 10 m Keck I Telescope and efficient HIRES echelle spectrograph, we derive abundances of several elements in subgiants near the M92 turnoff. As a consistency check, we also analyze the metal-poor field star HD 140283 and find an Fe abundance in fine agreement with …
Early Evolution of the Galactic Halo Revealed from Hipparcos Observations of Metal-poor Stars
Yoshii, Yuzuru; Chiba, Masashi
The kinematics of 122 red giant and 124 RR Lyrae stars in the solar neighborhood are studied using accurate measurements of their proper motions obtained by the Hipparcos astrometry satellite, combined with their published photometric distances, metal abundances, and radial velocities. A majority of these sample stars have metal abundances of [Fe/…
Hubble Space Telescope Observations of the Draco Dwarf Spheroidal Galaxy
Ballester, Gilda E.; Crisp, David; Grillmair, Carl J. +15 more
We present an F606W-F814W color-magnitude diagram for the Draco dwarf spheroidal galaxy based on Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images. The luminosity function is well sampled to ~3 mag below the turnoff. We see no evidence for multiple turnoffs and conclude that, at least over the field of view of the WFPC2, star for…