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The IRX–β Relation: Insights from Simulations

Safarzadeh, Mohammadtaher and Hayward, Christopher C. and Ferguson, Henry C. (2017) The IRX–β Relation: Insights from Simulations. Astrophysical Journal, 840 (1). Art. No. 15. ISSN 1538-4357.

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We study the relationship between the UV continuum slope and infrared excess (IRX ≡ L_(IR)/L_(FUV)) predicted by performing dust radiative transfer on a suite of hydrodynamical simulations of galaxies. Our suite includes both isolated disk galaxies and mergers intended to be representative of galaxies at both z ~ 0 and z ~ 2-3. Our low-redshift systems often populate a region around the locally calibrated Meurer et al. relation but move above the relation during merger-induced starbursts. Our high-redshift systems are blue and IR luminous and therefore lie above the Meurer et al. relation. The value of β strongly depends on the dust type used in the RT simulation: Milky-Way-type dust leads to significantly more negative (bluer) slopes compared with Small-Magellanic-Cloud-type dust. The effect on β due to variations in the dust composition with galaxy properties or redshift is the dominant model uncertainty. The dispersion in β is anticorrelated with specific star formation rate (sSFR) and tends to be higher for the z ~ 2-3 simulations. In the actively star-forming z ~ 2-3 simulated galaxies, dust attenuation dominates the dispersion in β, whereas in the z ~ 0 simulations, the contributions of star formation history (SFH) variations and dust are similar. For low-sSFR systems at both redshifts, SFH variations dominate the dispersion. Finally, the simulated z ~ 2-3 isolated disks and mergers both occupy a region in the IRX-β plane consistent with observed z ~ 2-3 dusty star-forming galaxies (DSFGs). Thus, contrary to some claims in the literature, the blue colors of high-z DSFGs do not imply that they are short-lived starbursts.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hayward, Christopher C.0000-0003-4073-3236
Ferguson, Henry C.0000-0001-7113-2738
Additional Information:© 2017 The American Astronomical Society. Received 2016 April 25; revised 2017 April 3; accepted 2017 April 6; published 2017 April 28. We thank Patrik Jonsson for insightful discussions. We are thankful to Caitlin Casey for providing us with data in electronic form. The Flatiron Institute is supported by the Simons Foundation. C.C.H. is grateful to the Gordon and Betty Moore Foundation for financial support. This work was partially supported by NASA's Astrophysics Data Analysis Program under grant NNX15AE54G. The computations in this paper were run on the Odyssey cluster supported by the FAS Division of Science, Research Computing Group at Harvard University. This research has made use of NASA's Astrophysics Data System Bibliographic Services and the preprint server.
Funding AgencyGrant Number
Simons FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Harvard UniversityUNSPECIFIED
Subject Keywords:dust, extinction – infrared: galaxies – radiative transfer – ultraviolet: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20170428-130941321
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Official Citation:Mohammadtaher Safarzadeh et al 2017 ApJ 840 15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77060
Deposited By: Tony Diaz
Deposited On:28 Apr 2017 20:29
Last Modified:14 Dec 2019 05:57

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