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A Study of Nine High-Redshift Clusters of Galaxies. III. Hubble Space Telescope Morphology of Clusters 0023+0423 and 1604+4304
Schneider, Donald P.; Postman, Marc; Hoessel, John G. +4 more
We present a detailed morphological analysis of the galaxy populations in the first two clusters to be completed in an extensive observational study of nine high-redshift clusters of galaxies. These two clusters, Cl 0023+0423 and Cl 1604+4304, are at redshifts of z = 0.84 and z = 0.90, respectively. The morphological studies are based on high angu…
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…
Adiabatic Deceleration of Solar Energetic Particles as Deduced from Monte Carlo Simulations of Interplanetary Transport
Vainio, R.; Torsti, J.; Kocharov, L. +1 more
Monte Carlo simulations of interplanetary transport are employed to study adiabatic energy losses of solar protons during propagation in the interplanetary medium. We consider four models. The first model is based on the diffusion-convection equation. Three other models employ the focused transport approach. In the focused transport models, we sim…
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
A Search for Star Clusters from the HIPPARCOS Data
van Leeuwen, Floor; Kozhurina-Platais, Vera; Platais, Imants
We present results of a search for nearby star clusters and associations using Hipparcos Catalogue data, restricting the sample to stars with parallaxes above 2 mas (d <~ 500 pc). Two new OB associations have been identified in the Carina-Vela and Cepheus-Cygnus-Lyra-Vulpecula regions. A very probable new open cluster has been discovered in Car…
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…
Nearby Young Solar Analogs. I. Catalog and Stellar Characteristics
Gaidos, Eric J.
We present a catalog of 38 young solar analogs within 25 pc, stars that are uniquely well suited for observations of their circumstellar environments to improve our understanding of conditions within the solar system during the Hadean/early Archean eons (prior to 3.8 Gyr ago). These G and early K stars were selected from the Hipparcos astrometric …
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…