Highly ionized gas in the Galactic disk: The L = 295 deg, b,= 0 deg interarm direction
1994; IOP Publishing; Volume: 434; Linguagem: Inglês
10.1086/174722
ISSN1538-4357
Autores Tópico(s)Atmospheric Ozone and Climate
Resumoview Abstract Citations (13) References (66) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Highly Ionized Gas in the Galactic Disk: The L = 295 degrees , B = 0 degrees Interarm Direction Sembach, Kenneth R. Abstract I present new high-resolution measurements of ultraviolet interstellar absorption lines toward three distant stars in the Galactic disk in the general direction l = 295 deg, b = 0 deg. The high ionization lines of Si IV and C IV toward HD 100276, HD 103779, and HD 104705 show substantial variations on angular scales of less than 1 deg, or about 50-100 pc at the distance of the stars. The Si IV and C IV midplane densities derived for HD 100276 and HD 103779 are No (Si IV) approximately = 1.3 x 10-9 cm-3 and no(C IV) approximately = 4.5 x 10-9 cvm-3, approximately a factor of 2-3 lower than the Galactic averages. Toward HD 104705, the Si IV midplane density is near the average value, but the C IV midplane density is a factor of 3 higher than average. The integrated C IV and Si IV ratios along the HD 100276 and HD 100379 sight lines are similar to the N(C IV)/N(Si IV) = 3.6 +/- 1.3 ratio for a sample of halo stars. For the HD 104705 sight line, N(C IV)/N(Si IV) = 11 and N(C IV)/N(N V) greater than 10. Turbulent mixing layers provide a possible source for the observed absorption along the three sight lines as does gas associated with cooling flows. If mixing layers are the primary source of the absorption along the disk sight lines, then the entrainment velocity of the hot gas is approximately 100 km/s and the post mixed gas temperature is approximately 2 x 105 K; same differences may exist for these mixing layers compared to those inferred for gas toward the Galactic poles. Current models of cooling, hot gas in supernova remnants, and magnetized conduction fronts do not accurately describe the high ion properties toward the disk stars in this study. Publication: The Astrophysical Journal Pub Date: October 1994 DOI: 10.1086/174722 Bibcode: 1994ApJ...434..244S Keywords: Absorption Spectra; Galactic Rotation; Galactic Structure; Interstellar Matter; Ionized Gases; Milky Way Galaxy; Stellar Mass Accretion; Ultraviolet Absorption; Hubble Space Telescope; Ionic Collisions; Iue; Photoionization; Satellite-Borne Instruments; Spectrographs; Astronomy; ISM: ABUNDANCES; STARS: INDIVIDUAL HENRY DRAPER NUMBER: HD 100276; STARS: INDIVIDUAL HENRY DRAPER NUMBER: HD 103779; STARS: INDIVIDUAL HENRY DRAPER NUMBER: HD 104705; TURBULENCE; ULTRAVIOLET: ISM full text sources ADS | data products SIMBAD (4) MAST (2) INES (1) ESA (1)
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