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Which galaxies dominate the neutral gas content of the Universe?

Lagos, C.D.P.; Baugh, C.M.; Zwaan, M.A.; Lacey, C.G.; Gonzalez-Perez, V.; Power, C.; Swinbank, A.M.; van Kampen, E.

Which galaxies dominate the neutral gas content of the Universe? Thumbnail


C.D.P. Lagos

M.A. Zwaan

V. Gonzalez-Perez

C. Power

E. van Kampen


We study the contribution of galaxies with different properties to the global densities of star formation rate (SFR), atomic (H I) and molecular hydrogen (H2) as a function of redshift. We use the GALFORM model of galaxy formation, which is set in the Λ cold dark matter (ΛCDM) framework. This model includes a self-consistent calculation of the SFR, which depends on the H2 content of galaxies. The predicted SFR density and how much of this is contributed by galaxies with different stellar masses and infrared luminosities are in agreement with observations. The model predicts a modest evolution of the H I density at z < 3, which is also in agreement with the observations. The H I density is predicted to be always dominated by galaxies with SFR < 1 M⊙ yr−1. This contrasts with the H2 density, which is predicted to be dominated by galaxies with SFR >10 M⊙ yr−1 at z > 1. Current high-redshift galaxy surveys are limited to detect carbon monoxide in galaxies with SFR ≳ 30 M⊙ yr−1, which in our model make up, at most, 20 per cent of the H2 in the universe. In terms of stellar mass, the predicted H2 density is dominated by massive galaxies, Mstellar > 1010 M⊙, while the H I density is dominated by low-mass galaxies, Mstellar < 109 M⊙. In the context of upcoming neutral gas surveys, we suggest that the faint nature of the galaxies dominating the H I content of the Universe will hamper the identification of optical counterparts, while for H2, we expect follow-up observations of molecular emission lines of already existing galaxy catalogues to be able to uncover the H2 density of the Universe.

Journal Article Type Article
Acceptance Date Feb 7, 2014
Online Publication Date Mar 16, 2014
Publication Date May 1, 2014
Deposit Date May 16, 2014
Publicly Available Date Jun 20, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 440
Issue 1
Pages 920-941
Keywords Stars: formation, Galaxies: evolution, Galaxies: formation, Galaxies: ISM.
Public URL


Published Journal Article (1.6 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.

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