Search Publications
Galaxy-Galaxy Lensing in the Hubble Deep Field: The Halo Tully-Fisher Relation at Intermediate Redshift
Gwyn, Stephen D. J.; Hudson, Michael J.; Dahle, Håkon +1 more
A tangential distortion of background source galaxies around foreground lens galaxies in the Hubble Deep Field is detected at the 99.3% confidence level. An important element of our analysis is the use of photometric redshifts to determine distances of lens and source galaxies and rest-frame B-band luminosities of the lens galaxies. The lens galax…
The Relationship between Galaxies and Low-Redshift Weak Lyα Absorbers in the Directions of H1821+643 and PG 1116+215
Tripp, Todd M.; Savage, Blair D.; Lu, Limin
To study the nature of low-z Lyα absorbers in the spectra of QSOs, we have obtained high signal-to-noise ratio (S/N) UV spectra of H1821+643 (zem = 0.297) and PG 1116+215 (zem = 0.177) with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope. The spectra have minimum S/Ns of ~70-100 and 3 σ limiting equival…
The Distance to the Large Magellanic Cloud from the Eclipsing Binary HV 2274
Ribas, I.; Fitzpatrick, E. L.; Guinan, E. F. +6 more
The distance to the Large Magellanic Cloud (LMC) is crucial for the calibration of the cosmic distance scale. We derive a distance to the LMC based on an analysis of ground-based photometry and Hubble Space Telescope (HST)-based spectroscopy and spectrophotometry of the LMC-eclipsing binary system HV 2274. Analysis of the optical light curve and t…
Detection of Abundant CO2 Ice in the Quiescent Dark Cloud Medium toward Elias 16
de Graauw, Th.; Prusti, T.; van Dishoeck, E. F. +9 more
We report the first detection of solid carbon dioxide (CO2) in quiescent regions of a dark cloud in the solar neighborhood, a result that has important implications for models of ice formation and evolution in the interstellar medium. The K-type field star Elias 16 was previously known to display solid-state absorption features of H
Testing the White Dwarf Mass-Radius Relation with HIPPARCOS
Provencal, J. L.; Shipman, H. L.; Thejll, P. +1 more
We present the Hipparcos parallaxes and resulting radii for 10 white dwarfs in visual binaries or common proper-motion systems and 11 field white dwarfs. For bright stars, Hipparcos parallaxes have uncertainties approaching 1 mas and are thus considerably more accurate than earlier ground-based parallaxes. Overall, our results support the predicti…
The Slope of the Cluster Elliptical Red Sequence: A Probe of Cluster Evolution
Yee, H. K. C.; Kodama, Tadayuki; Gladders, Michael D. +1 more
The current formation models for cluster elliptical galaxies, which incorporate a mechanism for the metallicity enhancement of massive elliptical galaxies, predict a change in the observed slope of the red sequence of elliptical galaxies as a function of redshift. This change occurs primarily because the metal-rich galaxies become redder faster th…
A Tentative Detection of the Cosmic Infrared Background at 3.5 µm from COBE/DIRBE Observations
Dwek, E.; Arendt, R. G.
Foreground emission and scattered light from interplanetary dust (IPD) particles and emission from Galactic stellar sources are the greatest obstacles to determining the cosmic infrared background (CIB) from diffuse sky measurements in the ~1-5 µm range. We use ground-based observational limits on the K-band intensity of the CIB in conjuncti…
Evolved Massive Stars in the Local Group. II. A New Survey for Wolf-Rayet Stars in M33 and Its Implications for Massive Star Evolution: Evidence of the ``Conti Scenario'' in Action
Massey, Philip; Johnson, Olivia
We expect the evolution of massive stars to be strongly influenced by mass loss and hence to be sensitive to metallicity. It should be possible to test this ``Conti scenario'' be comparing the populations of evolved massive stars among the Local Group galaxies, but such investigations have been hampered by incompleteness. In a previous paper, we p…
The Mass-to-Light Ratio of Early-Type Galaxies: Constraints from Gravitational Lensing in the Rich Cluster AC 114
Smail, Ian; Ellis, Richard S.; Kneib, Jean-Paul +1 more
We present a new wide-field image of the distant cluster AC 114 (z = 0.31) obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. This image considerably extends our knowledge of the lensing properties of the cluster beyond that derived earlier from a single WFPC1 pointing. In conjunction with published ground-based s…
Measuring the Sun's Eigenfrequencies from Velocity and Intensity Helioseismic Spectra: Asymmetrical Line Profile-fitting Formula
Kosovichev, A. G.; Nigam, R.
Solar eigenfrequencies are generally determined by fitting a Lorentzian to the spectral lines in the power spectrum. This assumes that the spectral line is symmetric. Recent observations from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory have indicated that the power spectra of p-modes show varying amounts of a…