Search Publications
On the Far-Infrared Emission of Quasars
Haas, Martin; Meisenheimer, Klaus; Chini, Rolf +4 more
Infrared spectral energy distributions between 4.8 and 200 µm are presented for a subsample of 10 quasars and radio galaxies from the European Central Quasar Programme observed with the Infrared Space Observatory. For three of the sources, this represents the first far-infrared detection. The spectral energy distributions (SEDs) reveal signa…
Acoustic Power Maps of Solar Active Regions
Brown, Timothy M.; Hindman, Bradley W.
Using observations made by the Michelson Doppler Imager (MDI), we find that within solar active regions the spatial distributions of Doppler velocity power and continuum intensity power differ. The oscillation power within any pixel is a strong function of the magnetic field strength within that pixel. The amplitudes of oscillations with frequenci…
A ``Short'' Distance to the Large Magellanic Cloud With the Hipparcos Calibrated Red Clump Stars
Zaritsky, D.; Stanek, K. Z.; Harris, J.
Following an approach developed by Paczyński & Stanek, we derive a distance to the Large Magellanic Cloud (LMC) by comparing red clump stars from the Hipparcos catalog with the red clump stars observed in two fields in the LMC that were selected from the ongoing photometric survey of the Magellanic Clouds to lie in low-extinction regions. The …
Molecular Gas in the Eagle Nebula
Pound, Marc W.
We present the first images of the molecular gas in the Eagle Nebula. Our maps of 12CO (1-0), 13CO (1-0), and 12C18O (1-0) emission, which have about 10" (~0.1 pc) resolution, reveal a molecular cloud being demolished by the intense activity of nearby O stars. Velocity gradients in the molecular gas reac…
The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field
Lanzetta, Kenneth M.; Pascarelle, Sebastian M.; Fernández-Soto, Alberto
Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star formation rate density, of the universe at redshifts 1<z<2. We use photometric redshifts of galaxies in the HDF to determine the comoving UV luminosity density, and we find that, when…
Discovery of z = 0.0912 and z = 0.2212 Damped Lyα Absorption-Line Systems Toward the Quasar OI 363: Limits on the Nature of Damped Lyα Galaxies
Turnshek, David A.; Rao, Sandhya M.
The discovery of a zabs=0.0912 damped Lyα absorption-line system in the Hubble Space Telescope Faint Object Spectrograph ultraviolet spectrum of the quasar OI 363 (0738+313) is reported. This is the lowest redshift quasar-damped Lyα system known. Its neutral hydrogen column density is N(H I) =1.5+/-0.2×1021 atoms cm-2
The Kinematic Composition of Mg II Absorbers
Charlton, Jane C.; Churchill, Christopher W.
The study of galaxy evolution using quasar absorption lines requires an understanding of what components of galaxies and their surroundings are contributing to the absorption in various transitions. This paper considers the kinematic composition of the class of 0.4 < z < 1.0 Mg II absorbers, particularly addressing the question of what fract…
Non-Maxwellian Redistribution in Solar Coronal Lyα Emission
Cranmer, Steven R.
This paper presents theoretical models of H I Lyα emission from the extended solar corona, taking into account various plasma kinetic effects that induce departures from Maxwellian velocity distributions. Such phenomena as suprathermal tails, strong temperature anisotropies, and skewed or double-peaked distributions have been observed in the solar…
An Optical/Near-Infrared Study of Radio-loud Quasar Environments. II. Imaging Results
Hall, Patrick B.; Green, Richard F.
We have previously reported a significant excess of K >~ 19 galaxies in the fields of a sample of 31 z = 1-2 quasars (Hall, Green, & Cohen). Here we examine the properties of this excess galaxy population using optical and near-IR imaging. The excess occurs on two spatial scales. One component lies at θ < 40" from the quasars and is sign…
The Rapid Decay of the Optical Emission from GRB 980326 and Its Possible Implications
Piro, L.; Veilleux, S.; Pian, E. +39 more
We report the discovery of the optical counterpart to GRB 980326. Its rapid optical decay can be characterized by a power law with exponent -2.10+/-0.13 and a constant underlying source at Rc=25.5+/-0.5. Its optical colors 2.1 days after the burst imply a spectral slope of -0.66+/-0.70. The γ-ray spectrum as observed with BATSE shows th…