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Simulating High-Redshift Disk Galaxies: Applications to Long Duration Gamma-Ray Burst Hosts

Published online by Cambridge University Press:  01 June 2008

Brant E. Robertson*
Affiliation:
Kavli Institute for Cosmological Physics, and Department of Astronomy and Astrophysics, University of Chicago, 933 East 56th Street, Chicago, IL 60637, USA email: [email protected] Enrico Fermi Institute, 5640 South Ellis Avenue, Chicago, IL 60637, USA Spitzer Fellow
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Abstract

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The efficiency of star formation governs many observable properties of the cosmological galaxy population, yet many current models of galaxy formation largely ignore the important physics of star formation and the interstellar medium (ISM). Using hydrodynamical simulations of disk galaxies that include a treatment of the molecular ISM and star formation in molecular clouds (Robertson & Kravtsov 2008), we study the influence of star formation efficiency and molecular hydrogen abundance on the properties of high-redshift galaxy populations. In this work, we focus on a model of low-mass, star forming galaxies at 1 ≲ z ≲ 2 that may host long duration gamma-ray bursts (GRBs). Observations of GRB hosts have revealed a population of faint systems with star formation properties that often differ from Lyman-break galaxies (LBGs) and more luminous high-redshift field galaxies. Observed GRB sightlines are deficient in molecular hydrogen, but it is unclear to what degree this deficiency owes to intrinsic properties of the galaxy or the impact the GRB has on its environment. We find that hydrodynamical simulations of low-stellar mass systems at high-redshifts can reproduce the observed star formation rates and efficiencies of GRB host galaxies at redshifts 1 ≲ z ≲ 2. We show that the compact structure of low-mass high-redshift GRB hosts may lead to a molecular ISM fraction of a few tenths, well above that observed in individual GRB sightlines. However, the star formation rates of observed GRB host galaxies imply molecular gas masses of 108 – 109M similar to those produced in the simulations, and may therefore imply fairly large average H2 fractions in their ISM.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2009

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