The IRX–β relation of high-redshift galaxies
Abstract
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.
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 (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_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.Attached Files
Published - stab096.pdf
Accepted Version - 2009.13522.pdf
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Additional details
- Eprint ID
- 109334
- Resolver ID
- CaltechAUTHORS:20210602-072448048
- University of Zurich
- Swiss National Science Foundation (SNSF)
- 157591
- Swiss National Science Foundation (SNSF)
- 194814
- NASA
- SMD-14-5189
- NASA
- SMD-15-5950
- NASA
- SMD-16-7561
- NASA
- SMD-17-1204
- NSF
- AST-120025
- NSF
- AST-140023
- NSF
- AST-150045
- Swiss National Supercomputing Centre (CSCS)
- s697
- Swiss National Supercomputing Centre (CSCS)
- s698
- NSF
- AST-1715206
- NSF
- AST-1908137
- NSF
- AST-1909153
- NASA Hubble Fellowship
- HST-AR-15043.001
- NSF
- AST-1715101
- Cottrell Scholar of Research Corporation
- NSF
- AST-1517491
- NSF
- AST-1715216
- NSF
- AST-1652522
- NASA
- 17-ATP17-0067
- NASA Hubble Fellowship
- HST-AR-14562.001
- Alfred P. Sloan Foundation
- NASA
- NNX14AH35G
- NSF
- AST-1411920
- NSF
- AST-1455342
- Munich Institute for Astro- and Particle Physics (MIAPP)
- Deutsche Forschungsgemeinschaft (DFG)
- Flatiron Institute
- Simons Foundation
- Created
-
2021-06-02Created from EPrint's datestamp field
- Updated
-
2021-06-02Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, TAPIR