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Star formation in galaxy mergers: ISM turbulence, dense gas excess, and scaling relations for disks and starbusts


Bournaud, F; Powell, L C; Chapon, D; Teyssier, R (2010). Star formation in galaxy mergers: ISM turbulence, dense gas excess, and scaling relations for disks and starbusts. Proceedings of the International Astronomical Union, 6(S271):160-169.

Abstract

Galaxy interactions and mergers play a significant, but still debated and poorly understood role in the star formation history of galaxies. Numerical and theoretical models cannot yet explain the main properties of merger-induced starbursts, including their intensity and their spatial extent. Usually, the mechanism invoked in merger-induced starbursts is a global inflow of gas towards the central kpc, resulting in a nuclear starburst. We show here, using high-resolution AMR simulations and comparing to observations of the gas component in mergers, that the triggering of starbursts also results from increased ISM turbulence and velocity dispersions in interacting systems. This forms cold gas that are denser and more massive than in quiescent disk galaxies. The fraction of dense cold gas largely increases, modifying the global density distribution of these systems, and efficient star formation results. Because the starbursting activity is not just from a global compacting of the gas to higher average surface densities, but also from higher turbulence and fragmentation into massive and dense clouds, merging systems can enter a different regime of star formation compared to quiescent disk galaxies. This is in quantitative agreement with recent observations suggesting that disk galaxies and starbursting systems are not the low-activity end and high-activity end of a single regime, but actually follow different scaling relations for their star formation.

Galaxy interactions and mergers play a significant, but still debated and poorly understood role in the star formation history of galaxies. Numerical and theoretical models cannot yet explain the main properties of merger-induced starbursts, including their intensity and their spatial extent. Usually, the mechanism invoked in merger-induced starbursts is a global inflow of gas towards the central kpc, resulting in a nuclear starburst. We show here, using high-resolution AMR simulations and comparing to observations of the gas component in mergers, that the triggering of starbursts also results from increased ISM turbulence and velocity dispersions in interacting systems. This forms cold gas that are denser and more massive than in quiescent disk galaxies. The fraction of dense cold gas largely increases, modifying the global density distribution of these systems, and efficient star formation results. Because the starbursting activity is not just from a global compacting of the gas to higher average surface densities, but also from higher turbulence and fragmentation into massive and dense clouds, merging systems can enter a different regime of star formation compared to quiescent disk galaxies. This is in quantitative agreement with recent observations suggesting that disk galaxies and starbursting systems are not the low-activity end and high-activity end of a single regime, but actually follow different scaling relations for their star formation.

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Additional indexing

Item Type:Journal Article, not refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:2010
Deposited On:19 Feb 2012 19:45
Last Modified:05 Apr 2016 15:21
Publisher:Cambridge University Press
ISSN:1743-9213 (P) 1743-9221 (E)
Additional Information:Published online: 12 August 2011. - Copyright: Cambridge University Press. - Proceedings of IAU Symposium 271 (Astrophysical Dynamics: From Stars to Galaxies), June 21-25, 2010, Nice, France
Publisher DOI:10.1017/S1743921311017571
Related URLs:http://arxiv.org/abs/1012.5227
http://irfu.cea.fr/Projets/IAUSymp271/ (Organisation)
Permanent URL: http://doi.org/10.5167/uzh-54779

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