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

Published online by Cambridge University Press:  12 August 2011

Frédéric Bournaud ,
Leila C. Powell ,
Damien Chapon  and
Romain Teyssier
Frédéric Bournaud
Affiliation:
CEA, IRFU, SAp – CEA Saclay, F-91191 Gif-sur-Yvette, France. email: [email protected]
Leila C. Powell
Affiliation:
CEA, IRFU, SAp – CEA Saclay, F-91191 Gif-sur-Yvette, France. email: [email protected]
Damien Chapon
Affiliation:
CEA, IRFU, SAp – CEA Saclay, F-91191 Gif-sur-Yvette, France. email: [email protected]
Romain Teyssier
Affiliation:
CEA, IRFU, SAp – CEA Saclay, F-91191 Gif-sur-Yvette, France. email: [email protected]
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Abstract

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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.

Keywords

galaxies: formationgalaxies: mergersgalaxies: star formation
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S271: Astrophysical Dynamics: From Stars to Galaxies , June 2010 , pp. 160 - 169
Copyright
Copyright © International Astronomical Union 2011

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