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What shapes the galaxy mass function? Exploring the roles of supernova-driven winds and active galactic nuclei

Bower, R. G. and Benson, A. J. and Crain, Robert A. (2012) What shapes the galaxy mass function? Exploring the roles of supernova-driven winds and active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 422 (4). pp. 2816-2840. ISSN 0035-8711. doi:10.1111/j.1365-2966.2012.20516.x.

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The observed stellar mass function (SMF) is very different to the halo mass function predicted by Λ cold dark matter (ΛCDM), and it is widely accepted that this is due to energy feedback from supernovae and black holes. However, the strength and form of this feedback is not understood. In this paper, we use the phenomenological model galform to explore how galaxy formation depends on the strength and halo mass dependence of feedback. We focus on 'expulsion' models in which the wind mass loading, β, is proportional to 1/v^n_(disc), with n= 0, 1, 2 and contrast these models with the successful Bower et al. model (B8W7), for which β α 1/v^(3.2)_(disc). A crucial development is that our code explicitly accounts for the recapture of expelled gas as the system’s halo mass (and thus gravitational potential) increases. While models with high wind speed and mass loading result in a poor match to the observed SMF, a model with slower wind speed matches the flat portion of the SMF at M_★∼ 10^9–10^(11) h^(−1) M_⊙. When combined with active galactic nucleus feedback, the model provides a good description of the observed SMF above 10^9 h^(−1) M_⊙. In order to explore the impact of different feedback schemes further, we examine how the expulsion models compare with a further range of observational data, contrasting the results with the B8W7 model. In the expulsion models, the brightest galaxies are assembled more recently, and the specific star formation rates of galaxies decrease strongly with decreasing stellar mass. The expulsion models tend to have a cosmic star formation density that is dominated by lower mass galaxies at z= 1–3, and dominated by high-mass galaxies at low redshift. These trends are in conflict with observational data, but the comparison highlights some deficiencies of the B8W7 model also. The experiments in this paper not only give us important physical insight into the impact of the feedback process on the formation histories of galaxies, but the strong mass dependence of feedback adopted in B8W7 still appears to provide the most promising description of the observed Universe.

Item Type:Article
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Benson, A. J.0000-0001-5501-6008
Additional Information:© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 January 6. Received 2012 January 6; in original form 2011 August 8. Article first published online: 24 Apr 2012. We thank our collaborators who have helped to develop the GALFORM project, Shaun Cole, Carlton Baugh, Cedric Lacey, Carlos Frenk, Claudia Lagos and Nikos Fanidakis. We thank Ivan Baldry for allowing us access to pre-release data on the galaxy mass function from the GAMA survey, and thank the anonymous referee for thoughtful comments. AJB acknowledges the support of the Gordon & Betty Moore Foundation, RAC is supported by the Australian Research Council via a Discovery Project grant and RGB thanks the STFC for support through the rolling grant scheme.
Group:Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Australian Research Council Discovery Project grantsUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords: galaxies: evolution; galaxies: formation
Issue or Number:4
Record Number:CaltechAUTHORS:20120620-075426733
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Official Citation:Bower, R. G., Benson, A. J. and Crain, R. A. (2012), What shapes the galaxy mass function? Exploring the roles of supernova-driven winds and active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 422: 2816–2840. doi: 10.1111/j.1365-2966.2012.20516.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31967
Deposited By: Ruth Sustaita
Deposited On:20 Jun 2012 15:26
Last Modified:09 Nov 2021 20:02

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