Search Publications
The Metallicity and Dust Content of HVC 287.5+22.5+240: Evidence for a Magellanic Clouds Origin
Sembach, Kenneth R.; Savage, Blair D.; Wakker, Bart P. +3 more
We estimate the abundances of S and Fe in the high-velocity cloud HVC 287.5+22.5+240, which has a velocity of 240 km s^-1 with respect to the local standard of rest and Galactic direction l ~ 287 deg and b ~ 23 deg. The measurements are based on UV absorption lines of these elements in the Hubble Space Telescope spectrum of NGC 3783, a background …
A Blind Test of Photometric Redshift Prediction
Dickinson, Mark; Sawicki, Marcin; Hogg, David W. +16 more
Results of a blind test of photometric redshift predictions against spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck Telescope are presented. The best photometric redshift schemes predict spectroscopic redshifts with a redshift accuracy of Deltaz < 0.1 for more than 68% of sources and with Deltaz < 0.3 for 100%,…
Radii and Effective Temperatures for K and M Giants and Supergiants. II.
van Belle, G. T.; Thompson, R. R.; Dyck, H. M.
We present new interferometric observations for 74 luminous red stars, made in the near-infrared. We show that our 2.2 µm uniform-disk diameters agree with other near-infrared diameter determinations (lunar occultations and interferometers) for 22 stars measured in common with ours. From our new data, we derive effective temperatures that ar…
The Recent Star Formation History of GR 8 from Hubble Space Telescope Photometry of the Resolved Stars
Saha, A.; Gallagher, J.; Mateo, Mario +6 more
We have used the Hubble Space Telescope to observe the resolved stars in the dwarf irregular galaxy GR 8 (DDO 155, UGC 8091). The data consisted of dithered Wide Field Planetary Camera 2 images in three bands: F439W (1 hr), F555W (30 minutes), and F814W (30 minutes). The stellar photometry was extracted with a modified version of DoPHOT. Artificia…
Weak and Post-T Tauri Stars around B-Type Members of the Scorpius-Centaurus OB Association
Martín, E. L.
I report medium-resolution (FWHM = 1.9 Å) spectroscopic observations of six Hα emission-line stars proposed in 1993 by Meyer, Wilking, & Zinnecker to be T Tauri stars formed in the vicinity of the B1 giant sigma Sco, a bright member of the Sco-Cen OB association. Using spectroscopic criteria (spectral types, Hα and Li i equivalent widths), whi…
Dwarf Elliptical Galaxies in the M81 Group: The Structure and Stellar Populations of BK5N and F8D1
Da Costa, G. S.; Caldwell, Nelson; Seitzer, Patrick +1 more
The M81 Group is one of the nearest groups of galaxies, but its properties are quite different from those of the Local Group. It has therefore provided a different environment for the evolution of its member galaxies. We have carried out a CCD survey of the M81 Group to search for analogs to Local Group dwarf elliptical (dE) galaxies. All the M81 …
The Radio Properties of NGC 5253 and Its Unusual H II Regions
Turner, Jean L.; Beck, Sara C.; Ho, Paul T. P.
We present VLA images of the radio continuum emission of the starburst in NGC 5253 at wavelengths of 6, 3.6, and 2 cm, with resolutions of 1"-2", and at 20 cm with resolution of ~9". A spectral index map constructed from the 6 and 2 cm images indicates that thermal free-free emission from ionized gas, most of it from a single source, dominates the…
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.…