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Title: Coronal gas in the galaxy. II. A statistical analysis of O VI absorptions

Abstract

Results from the survey of interstellar O VI by Jenkins and by Jenkins and Meloy are analyzed to synthesize a global description of the properties of the coronal gas. Tests for correlations of column densities or velocities with properties of the target stars showed no evidence for a circumstellar origin for the absorption lines. An overall average density n (O VI) =2.8 x 10/sup -8/ cm/sup -3/ was found in the galactic plane, with a decrease which approximately follows exp (-z/300 pc) away from the plane.Fluctuations in column densities over various lines of sight suggest that existence of six hot gas regions kpc/sup -/1, randomly distributed in space, each with an O VI column density of about 10/sup 13/ cm/sup -2/. These regions account for an average density n (O VI) =2.1 x 10/sup -8/ cm/sup -3/; the remaining 7 x 10/sup -9/ cm/sup -3/ is produced by more sparsely distributed but thicker parcels of hot gas which are seen toward 10% of the stars. The statistics of radial velocity centroids and widths support the interpretation of distinct domains; each region has an internal velocity dispersion consistent with a Doppler broadening of a plasma at T> or approx. =2 xmore » 10/sup 5/ K (near the characteristic temperature for a maximum concentration of O VI in collisional equilibrium), while the regions themselves move about with a dispersion of radial velocities equal to 26 km s/sup -1/. Systematic motions of gas away from the galactic plane could not be seen, however.Excursions from the normal O VI per unit distance have no perceptible anicorrelation with deviations in reddening by cool interstellar coulds: a fact which suggests that the average filling factor of O VI gas is less than 20% if coronal gas really displaces the cooler material and does not have large variations in density and temperature.« less

Authors:
Publication Date:
Research Org.:
Princeton University Observatory
OSTI Identifier:
5041070
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophys. J.; (United States); Journal Volume: 220:1
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COSMIC GASES; SPATIAL DISTRIBUTION; OXYGEN IONS; COSMOCHEMISTRY; ABUNDANCE; CHEMICAL COMPOSITION; COSMIC RADIATION; INTERSTELLAR SPACE; MILKY WAY; RADIAL VELOCITY; STATISTICS; X RADIATION; CHARGED PARTICLES; CHEMISTRY; DISTRIBUTION; ELECTROMAGNETIC RADIATION; FLUIDS; GALAXIES; GASES; IONIZING RADIATIONS; IONS; MATHEMATICS; RADIATIONS; SPACE; VELOCITY; 640105* - Astrophysics & Cosmology- Galaxies

Citation Formats

Jenkins, E.B.. Coronal gas in the galaxy. II. A statistical analysis of O VI absorptions. United States: N. p., 1978. Web. doi:10.1086/155885.
Jenkins, E.B.. Coronal gas in the galaxy. II. A statistical analysis of O VI absorptions. United States. doi:10.1086/155885.
Jenkins, E.B.. Wed . "Coronal gas in the galaxy. II. A statistical analysis of O VI absorptions". United States. doi:10.1086/155885.
@article{osti_5041070,
title = {Coronal gas in the galaxy. II. A statistical analysis of O VI absorptions},
author = {Jenkins, E.B.},
abstractNote = {Results from the survey of interstellar O VI by Jenkins and by Jenkins and Meloy are analyzed to synthesize a global description of the properties of the coronal gas. Tests for correlations of column densities or velocities with properties of the target stars showed no evidence for a circumstellar origin for the absorption lines. An overall average density n (O VI) =2.8 x 10/sup -8/ cm/sup -3/ was found in the galactic plane, with a decrease which approximately follows exp (-z/300 pc) away from the plane.Fluctuations in column densities over various lines of sight suggest that existence of six hot gas regions kpc/sup -/1, randomly distributed in space, each with an O VI column density of about 10/sup 13/ cm/sup -2/. These regions account for an average density n (O VI) =2.1 x 10/sup -8/ cm/sup -3/; the remaining 7 x 10/sup -9/ cm/sup -3/ is produced by more sparsely distributed but thicker parcels of hot gas which are seen toward 10% of the stars. The statistics of radial velocity centroids and widths support the interpretation of distinct domains; each region has an internal velocity dispersion consistent with a Doppler broadening of a plasma at T> or approx. =2 x 10/sup 5/ K (near the characteristic temperature for a maximum concentration of O VI in collisional equilibrium), while the regions themselves move about with a dispersion of radial velocities equal to 26 km s/sup -1/. Systematic motions of gas away from the galactic plane could not be seen, however.Excursions from the normal O VI per unit distance have no perceptible anicorrelation with deviations in reddening by cool interstellar coulds: a fact which suggests that the average filling factor of O VI gas is less than 20% if coronal gas really displaces the cooler material and does not have large variations in density and temperature.},
doi = {10.1086/155885},
journal = {Astrophys. J.; (United States)},
number = ,
volume = 220:1,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 1978},
month = {Wed Feb 15 00:00:00 EST 1978}
}