COLD GAS ACCRETION BY HIGH-VELOCITY CLOUDS AND THEIR CONNECTION TO QSO ABSORPTION-LINE SYSTEMS

Journal Article · Thu May 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/750/2/165· OSTI ID:22034469

Richter, Philipp ^[1]

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1. Institut fuer Physik und Astronomie, Universitaet Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, 14476 Golm, Potsdam (Germany)

We combine H I 21 cm observations of the Milky Way, M31, and the local galaxy population with QSO absorption-line measurements to geometrically model the three-dimensional distribution of infalling neutral-gas clouds ('high-velocity clouds' (HVCs)) in the extended halos of low-redshift galaxies. We demonstrate that the observed distribution of HVCs around the Milky Way and M31 can be modeled by a radial exponential decline of the mean H I volume-filling factor in their halos. Our model suggests a characteristic radial extent of HVCs of R{sub halo} {approx} 50 kpc, a total H I mass in HVCs of {approx}10{sup 8} M{sub Sun }, and a neutral-gas accretion rate of {approx}0.7 M{sub Sun} yr{sup -1} for M31/Milky-Way-type galaxies. Using a Holmberg-like luminosity scaling of the halo size of galaxies we estimate R{sub halo} {approx} 110 kpc for the most massive galaxies. The total absorption cross-section of HVCs at z Almost-Equal-To 0 most likely is dominated by galaxies with total H I masses between 10{sup 8.5} and 10{sup 10} M{sub Sun }. Our model indicates that the H I disks of galaxies and their surrounding HVC population can account for 30%-100% of intervening QSO absorption-line systems with log N(H I) {>=} 17.5 at z Almost-Equal-To 0. We estimate that the neutral-gas accretion rate density of galaxies at low redshift from infalling HVCs is dM{sub Hi}/dt/dV{approx}0.022 M{sub sun} yr{sup -1} Mpc{sup -3}, which is close to the measured star formation rate density in the local universe. HVCs thus may play an important role in the ongoing formation and evolution of galaxies.

• OSTI ID: 22034469
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 750; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ASTRONOMY
ASTROPHYSICS
CROSS SECTIONS
GALACTIC EVOLUTION
LUMINOSITY
MASS
MILKY WAY
QUASARS
RED SHIFT
SPATIAL DISTRIBUTION
STAR EVOLUTION
STARS
THREE-DIMENSIONAL CALCULATIONS
UNIVERSE
VELOCITY