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Large-scale galactic turbulence: can self-gravity drive the observed H i velocity dispersions?


Agertz, O; Lake, G; Teyssier, R; Moore, B; Mayer, L; Romeo, A B (2009). Large-scale galactic turbulence: can self-gravity drive the observed H i velocity dispersions? Monthly Notices of the Royal Astronomical Society, 392(1):294-308.

Abstract

Observations of turbulent velocity dispersions in the H i component of galactic discs show a characteristic floor in galaxies with low star formation rates and within individual galaxies the dispersion profiles decline with radius. We carry out several high-resolution adaptive mesh simulations of gaseous discs embedded within dark matter haloes to explore the roles of cooling, star formation, feedback, shearing motions and baryon fraction in driving turbulent motions. In all simulations the disc slowly cools until gravitational and thermal instabilities give rise to a multiphase medium in which a large population of dense self-gravitating cold clouds are embedded within a warm gaseous phase that forms through shock heating. The diffuse gas is highly turbulent and is an outcome of large-scale driving of global non-axisymmetric modes as well as cloud–cloud tidal interactions and merging. At low star formation rates these processes alone can explain the observed H i velocity dispersion profiles and the characteristic value of ∼10 km s−1 observed within a wide range of disc galaxies. Supernovae feedback creates a significant hot gaseous phase and is an important driver of turbulence in galaxies with a star formation rate per unit area ≳10−3 M⊙ yr−1 kpc−2 .

Abstract

Observations of turbulent velocity dispersions in the H i component of galactic discs show a characteristic floor in galaxies with low star formation rates and within individual galaxies the dispersion profiles decline with radius. We carry out several high-resolution adaptive mesh simulations of gaseous discs embedded within dark matter haloes to explore the roles of cooling, star formation, feedback, shearing motions and baryon fraction in driving turbulent motions. In all simulations the disc slowly cools until gravitational and thermal instabilities give rise to a multiphase medium in which a large population of dense self-gravitating cold clouds are embedded within a warm gaseous phase that forms through shock heating. The diffuse gas is highly turbulent and is an outcome of large-scale driving of global non-axisymmetric modes as well as cloud–cloud tidal interactions and merging. At low star formation rates these processes alone can explain the observed H i velocity dispersion profiles and the characteristic value of ∼10 km s−1 observed within a wide range of disc galaxies. Supernovae feedback creates a significant hot gaseous phase and is an important driver of turbulence in galaxies with a star formation rate per unit area ≳10−3 M⊙ yr−1 kpc−2 .

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Uncontrolled Keywords:hydrodynamics; turbulence; galaxies: evolution; galaxies: formation; galaxies: general
Language:English
Date:January 2009
Deposited On:26 Feb 2010 12:44
Last Modified:07 Dec 2017 00:52
Publisher:Wiley-Blackwell
ISSN:0035-8711
Additional Information:The definitive version is available at www.blackwell-synergy.com
Publisher DOI:https://doi.org/10.1111/j.1365-2966.2008.14043.x
Related URLs:http://arxiv.org/abs/0810.1741

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