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Cosmic evolution of the atomic and molecular gas contents of galaxies

Lagos, Claudia del P. and Baugh, Carlton M. and Lacey, Cedric G. and Benson, Andrew J. and Kim, Han-Seek and Power, Chris (2011) Cosmic evolution of the atomic and molecular gas contents of galaxies. Monthly Notices of the Royal Astronomical Society, 418 (3). pp. 1649-1667. ISSN 0035-8711.

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We study the evolution of the cold gas content of galaxies by splitting the interstellar medium into its atomic and molecular hydrogen components, using the galaxy formation model galform in the Λ cold dark matter framework. We calculate the molecular-to-atomic hydrogen mass ratio, H_(2)/H i, in each galaxy using two different approaches, the pressure-based empirical relation of Blitz & Rosolowsky and the theoretical model of Krumholz, McKeee & Tumlinson, and apply them to consistently calculate the star formation rates of galaxies. We find that the model based on the Blitz & Rosolowsky law predicts an H i mass function, ^(12)CO (1–0) luminosity function, correlations between H_(2)/H i and stellar and cold gas mass, and infrared–^(12)CO molecule luminosity relation in good agreement with local and high-redshift observations. The H i mass function evolves weakly with redshift, with the number density of high-mass galaxies decreasing with increasing redshift. In the case of the H_2 mass function, the number density of massive galaxies increases strongly from z= 0 to 2, followed by weak evolution up to z= 4. We also find that H_(2)/H i of galaxies is strongly dependent on stellar and cold gas mass, and also on redshift. The slopes of the correlations between H_(2)/H i and stellar and cold gas mass hardly evolve, but the normalization increases by up to two orders of magnitude from z= 0 to 8. The strong evolution in the H_2 mass function and H_(2)/H i is primarily due to the evolution in the sizes of galaxies and, secondarily, in the gas fractions. The predicted cosmic density evolution of H i agrees with the observed evolution inferred from damped Lyα systems, and is always dominated by the H i content of low- and intermediate-mass haloes. We find that previous theoretical studies have largely overestimated the redshift evolution of the global H_(2)/H i due to limited resolution. We predict a maximum of ρH_2/ρH i ≈ 1.2 at z≈ 3.5.

Item Type:Article
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URLURL TypeDescription
Lagos, Claudia del P.0000-0003-3021-8564
Baugh, Carlton M.0000-0002-9935-9755
Benson, Andrew J.0000-0001-5501-6008
Additional Information:© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 Royal Astronomical Society. Accepted 2011 August 3. Received 2011 July 27; in original form 2011 May 10. Article first published online: 3 Nov. 2011. We thank Richard Bower, Ian Smail, Houjun Mo, Nicolas Tejos, Gabriel Altay, Estelle Bayet and Padeli Papadopoulos for useful comments and discussions, and Rachael Livermore and Matthew Bothwell for providing the observational data of the IR–CO relation and the H I and H2 scaling relations, respectively. We thank the anonymous referee for helpful suggestions that improved this work. CdPL gratefully acknowledges a STFC Gemini studentship. AJB acknowledges the support of the Gordon & Betty Moore Foundation. This work was supported by a rolling grant from the STFC. Part of the calculations for this paper were performed on the ICC Cosmology Machine, which is part of the DiRAC Facility jointly funded by the STFC, Large Facilities Capital Fund of BIS and Durham University.
Group:Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:stars: formation; galaxies: evolution; galaxies: formation; galaxies: ISM
Issue or Number:3
Record Number:CaltechAUTHORS:20120217-122730662
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Official Citation:Lagos, C. d. P., Baugh, C. M., Lacey, C. G., Benson, A. J., Kim, H.-S. and Power, C. (2011), Cosmic evolution of the atomic and molecular gas contents of galaxies. Monthly Notices of the Royal Astronomical Society, 418: 1649–1667. doi: 10.1111/j.1365-2966.2011.19583.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29368
Deposited By: Jason Perez
Deposited On:17 Feb 2012 22:23
Last Modified:09 Mar 2020 13:18

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