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Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution and implications for the IMF

Hayward, Christopher C. and Narayanan, Desika and Kereš, Dušan and Jonsson, Patrik and Hopkins, Philip F. and Cox, T. J. and Hernquist, Lars (2013) Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution and implications for the IMF. Monthly Notices of the Royal Astronomical Society, 428 (3). pp. 2529-2547. ISSN 1365-2966.

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High-redshift submillimetre galaxies (SMGs) are some of the most rapidly star-forming galaxies in the Universe. Historically, galaxy formation models have had difficulty explaining the observed number counts of SMGs. We combine a semi-empirical model with 3D hydrodynamical simulations and 3D dust radiative transfer to predict the number counts of unlensed SMGs. Because the stellar mass functions, gas and dust masses, and sizes of our galaxies are constrained to match observations, we can isolate uncertainties related to the dynamical evolution of galaxy mergers and the dust radiative transfer. The number counts and redshift distributions predicted by our model agree well with observations. Isolated disc galaxies dominate the faint (S_(1.1) ≲ 1 or S_(850) ≲ 2 mJy) population. The brighter sources are a mix of merger-induced starbursts and galaxy-pair SMGs; the latter subpopulation accounts for ∼30–50 per cent of all SMGs at all S_(1.1) ≳ 0.5 mJy (S_(850) ≳ 1 mJy). The mean redshifts are ∼3.0–3.5, depending on the flux cut, and the brightest sources tend to be at higher redshifts. Because the galaxy-pair SMGs will be resolved into multiple fainter sources by the Atacama Large Millimeter/submillimeter Array (ALMA), the bright ALMA counts should be as much as two times less than those observed using single-dish telescopes. The agreement between our model, which uses a Kroupa initial mass function (IMF), and observations suggests that the IMF in high-redshift starbursts need not be top heavy; if the IMF were top heavy, our model would overpredict the number counts. We conclude that the difficulty some models have reproducing the observed SMG counts is likely indicative of more general problems – such as an underprediction of the abundance of massive galaxies or a star formation rate and stellar mass relation normalization lower than that observed – rather than a problem specific to the SMG population.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hayward, Christopher C.0000-0003-4073-3236
Narayanan, Desika0000-0002-7064-4309
Kereš, Dušan0000-0002-1666-7067
Hopkins, Philip F.0000-0003-3729-1684
Hernquist, Lars0000-0001-6950-1629
Additional Information:© 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2012 October 15. Received 2012 October 9; in original form 2012 September 10. While this paper was being refereed, ALMA 870-μm number counts for the Extended Chandra Deep Field South were made publicly available (Karim et al. 2012). As predicted by our model, a significant fraction of the sources are resolved into multiple sources. Interestingly, all of the brightest sources (S_(870) > 12 mJy) are resolved into multiple sources. This intriguing result is in contrast with the predictions of our model and has not been predicted by any other model. We thank Andrew Benson, Romeel Davé, Mark Swinbank and Naoki Yoshida for comments on the manuscript; Scott Chapman, Michał Michałowski, Pierluigi Monaco, Alex Pope, Isaac Roseboom and Josh Younger for useful discussion; Carlton Baugh, Cedric Lacey, Fabio Fontanot, Gian-Luigi Granato, Vernesa Smolčić, Axel Weiß and Min Yun for providing data with which we have compared and for useful discussion and Volker Springel for providing the non-public version of GADGET-2 used for this work. DN acknowledges support from a National Science Foundation Grant (AST-1009452). DK was supported by NASA through Hubble Fellowship grant HST-HF-51276.01-A. PJ acknowledges support by a grant from the W. M. Keck Foundation. The simulations in this paper were performed on the Odyssey cluster supported by the FAS Research Computing Group at Harvard University.
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF-51276.01-A
W. M. Keck FoundationUNSPECIFIED
Harvard UniversityUNSPECIFIED
Subject Keywords:radiative transfer, stars: luminosity function, mass function, galaxies: high-redshift, galaxies: starburst, infrared: galaxies, submillimetre: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20200522-113949570
Persistent URL:
Official Citation:Christopher C. Hayward, Desika Narayanan, Dušan Kereš, Patrik Jonsson, Philip F. Hopkins, T. J. Cox, Lars Hernquist, Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution and implications for the IMF, Monthly Notices of the Royal Astronomical Society, Volume 428, Issue 3, 21 January 2013, Pages 2529–2547,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103415
Deposited By: George Porter
Deposited On:22 May 2020 19:03
Last Modified:22 May 2020 19:03

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