Cold gas accretion by high-velocity clouds and their connection to QSO Absorption-line systems
- 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-halo similar to 50 kpc, a total H I mass in HVCs of similar to 10(8) M-circle dot, and a neutral-gas accretion rate of similar to 0.7 M-circle dot yr(-1) for M31/Milky-Way-type galaxies. Using a Holmberg-like luminosity scaling of the halo size of galaxies we estimate R-halo similar to 110 kpc for the most massive galaxies. The total absorption cross-section of HVCs at z approximate to 0 most likely is dominated by galaxies with total H I masses between 10(8.5) and 10(10) M-circle dot. Our modelWe 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-halo similar to 50 kpc, a total H I mass in HVCs of similar to 10(8) M-circle dot, and a neutral-gas accretion rate of similar to 0.7 M-circle dot yr(-1) for M31/Milky-Way-type galaxies. Using a Holmberg-like luminosity scaling of the halo size of galaxies we estimate R-halo similar to 110 kpc for the most massive galaxies. The total absorption cross-section of HVCs at z approximate to 0 most likely is dominated by galaxies with total H I masses between 10(8.5) and 10(10) M-circle dot. 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 approximate to 0. We estimate that the neutral-gas accretion rate density of galaxies at low redshift from infalling HVCs is dM(H) (I)/dt/dV approximate to 0.022 M-circle dot yr(-1) Mpc(-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.…
Verfasserangaben: | Philipp RichterORCiDGND |
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DOI: | https://doi.org/10.1088/0004-637X/750/2/165 |
ISSN: | 0004-637X |
Titel des übergeordneten Werks (Englisch): | The astrophysical journal : an international review of spectroscopy and astronomical physics |
Verlag: | IOP Publ. Ltd. |
Verlagsort: | Bristol |
Publikationstyp: | Wissenschaftlicher Artikel |
Sprache: | Englisch |
Jahr der Erstveröffentlichung: | 2012 |
Erscheinungsjahr: | 2012 |
Datum der Freischaltung: | 26.03.2017 |
Freies Schlagwort / Tag: | Galaxy: halo; ISM: clouds; quasars: absorption lines |
Band: | 750 |
Ausgabe: | 2 |
Seitenanzahl: | 11 |
Organisationseinheiten: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
Peer Review: | Referiert |