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The IRX–β relation of high-redshift galaxies

Liang, Lichen and Feldmann, Robert and Hayward, Christopher C. and Narayanan, Desika and Çatmabacak, Onur and Kereš, Dušan and Faucher-Giguère, Claude-André and Hopkins, Philip F. (2021) The IRX–β relation of high-redshift galaxies. Monthly Notices of the Royal Astronomical Society, 502 (3). pp. 3210-3241. ISSN 0035-8711. doi:10.1093/mnras/stab096.

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The relation between infrared excess (IRX) and UV spectral slope (β_(UV)) is an empirical probe of dust properties of galaxies. The shape, scatter, and redshift evolution of this relation are not well understood, however, leading to uncertainties in estimating the dust content and star formation rates (SFRs) of galaxies at high redshift. In this study, we explore the nature and properties of the IRX–β_(UV) relation with a sample of z = 2–6 galaxies (⁠M∗ ≈ 10⁹−10¹²M⊙⁠) extracted from high-resolution cosmological simulations (MassiveFIRE) of the Feedback in Realistic Environments (FIRE) project. The galaxies in our sample show an IRX–βUV relation that is in good agreement with the observed relation in nearby galaxies. IRX is tightly coupled to the UV optical depth, and is mainly determined by the dust-to-star geometry instead of total dust mass, while β_(UV) is set both by stellar properties, UV optical depth, and the dust extinction law. Overall, much of the scatter in the IRX–β_(UV) relation of our sample is found to be driven by variations of the intrinsic UV spectral slope. We further assess how the IRX–β_(UV) relation depends on viewing direction, dust-to-metal ratio, birth-cloud structures, and the dust extinction law and we present a simple model that encapsulates most of the found dependencies. Consequently, we argue that the reported ‘deficit’ of the infrared/sub-millimetre bright objects at z ≳ 5 does not necessarily imply a non-standard dust extinction law at those epochs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Liang, Lichen0000-0001-9422-0095
Feldmann, Robert0000-0002-1109-1919
Hayward, Christopher C.0000-0003-4073-3236
Narayanan, Desika0000-0002-7064-4309
Kereš, Dušan0000-0002-1666-7067
Faucher-Giguère, Claude-André0000-0002-4900-6628
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 January 7. Received 2021 January 7; in original form 2020 October 8. Published: 14 January 2021. We thank the anonymous referee for the helpful comments that improve the clarity of this manuscript. This work has benefited from discussions with Pascal Oesch (Geneva), Nick Z. Scoville (Caltech), Xuejian (Jacob) Shen (Caltech), Marcel Neeleman (MPIA), Laura Sommovigo (Scuola Normale Superiore), and Andrea Ferrara (Scuola Normale Superiore). We thank Caitlin Casey for providing us with the data that are not publicly available for producing Fig. 4. LL would like to thank the hospitality of the Department of Astronomy of the University of Florida (UF), where part of this manuscript was improved. His research stay at UF was supported by the GRC Grant awarded by the University of Zurich. RF acknowledges financial support from the Swiss National Science Foundation (grant no. 157591 and 194814). Simulations were run with resources provided by the NASA High-End Computing (HEC) Programme. Additional computing support was provided by HEC allocations SMD-14-5189, SMD-15-5950, SMD-16-7561, SMD-17-1204, by NSF XSEDE allocations AST120025, AST140023, AST150045, by allocations s697, s698 at the Swiss National Supercomputing center (CSCS), and by S3IT resources at the University of Zurich. DN was supported by NSF grants AST-1715206, AST-1908137, and AST-1909153, as well as HST-AR-15043.001. DK acknowledges support from the NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522; by NASA through grant 17-ATP17-0067; by STScI through grant HST-AR-14562.001; and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. PFH was supported by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. This research was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the Deutsche Forschungsgemeinschaft (DFG) cluster of excellence ‘Origin and Structure of the Universe’. The Flatiron Institute is supported by the Simons Foundation. Data Availability Statement: The data underlying this article will be shared on reasonable request to the corresponding author.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
University of ZurichUNSPECIFIED
Swiss National Science Foundation (SNSF)157591
Swiss National Science Foundation (SNSF)194814
Swiss National Supercomputing Centre (CSCS)s697
Swiss National Supercomputing Centre (CSCS)s698
NASA Hubble FellowshipHST-AR-15043.001
Cottrell Scholar of Research CorporationUNSPECIFIED
NASA Hubble FellowshipHST-AR-14562.001
Alfred P. Sloan FoundationUNSPECIFIED
Munich Institute for Astro- and Particle Physics (MIAPP)UNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
Flatiron InstituteUNSPECIFIED
Simons FoundationUNSPECIFIED
Subject Keywords:dust, extinction – galaxies: evolution – galaxies: high-redshift – galaxies: ISM– infrared: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20210602-072448048
Persistent URL:
Official Citation:Lichen Liang, Robert Feldmann, Christopher C Hayward, Desika Narayanan, Onur Çatmabacak, Dušan Kereš, Claude-André Faucher-Giguère, Philip F Hopkins, The IRX–β relation of high-redshift galaxies, Monthly Notices of the Royal Astronomical Society, Volume 502, Issue 3, April 2021, Pages 3210–3241,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109334
Deposited By: Tony Diaz
Deposited On:02 Jun 2021 17:33
Last Modified:02 Jun 2021 17:33

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