Journal Article

Accretion of gas on to nearby spiral galaxies

F. Fraternali and J. J. Binney

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 386, issue 2, pages 935-944
Published in print May 2008 | ISSN: 0035-8711
Published online April 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13071.x
Accretion of gas on to nearby spiral galaxies

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We present evidence for cosmological gas accretion on to spiral galaxies in the local universe. The accretion is seen through its effects on the dynamics of the extraplanar neutral gas. The accretion rates that we estimate for two nearby spiral galaxies are of the order of their star formation rates. Our model shows that most of the extraplanar gas is produced by supernova feedback (galactic fountain) and only 10–20 per cent comes from accretion. The accreting material must have low specific angular momentum about the disc's spin axis, although the magnitude of the specific angular momentum vector can be higher. We also explore the effects of a hot corona on the dynamics of the extraplanar gas and find that it is unlikely to be responsible for the observed kinematical pattern and the source of accreted gas. However, the interaction with the fountain flow should profoundly affect the hydrodynamics of the corona.

Keywords: ISM: kinematics and dynamics; galaxies: evolution; galaxies: haloes; galaxies: individual: NGC 891; galaxies: individual: NGC 2403; galaxies: kinematics and dynamics

Journal Article.  8183 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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