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The ALMA Spectroscopic Survey Large Program : the infrared excess of z = 1.5–10 UV-selected galaxies and the implied high-redshift star formation history.

Bouwens, Rychard and González-López, Jorge and Aravena, Manuel and Decarli, Roberto and Novak, Mladen and Stefanon, Mauro and Walter, Fabian and Boogaard, Leindert and Carilli, Chris and Dudzevičiūtė, Ugnė and Smail, Ian and Daddi, Emanuele and da Cunha, Elisabete and Ivison, Rob and Nanayakkara, Themiya and Cortes, Paulo and Cox, Pierre and Inami, Hanae and Oesch, Pascal and Popping, Gergö and Riechers, Dominik and van der Werf, Paul and Weiss, Axel and Fudamoto, Yoshi and Wagg, Jeff (2020) 'The ALMA Spectroscopic Survey Large Program : the infrared excess of z = 1.5–10 UV-selected galaxies and the implied high-redshift star formation history.', Astrophysical journal., 902 (2). p. 112.

Abstract

We make use of sensitive (9.3 μJy beam−1 rms) 1.2 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra-Deep Field (ASPECS) large program to probe dust-enshrouded star formation from 1362 Lyman-break galaxies spanning the redshift range z = 1.5–10 (to ~7–28 M ⊙ yr−1 at 4σ over the entire range). We find that the fraction of ALMA-detected galaxies in our z = 1.5–10 samples increases steeply with stellar mass, with the detection fraction rising from 0% at 109.0 M ⊙ to ${85}_{-18}^{+9}$% at >1010 M ⊙. Moreover, on stacking all 1253 low-mass (<109.25 M ⊙) galaxies over the ASPECS footprint, we find a mean continuum flux of −0.1 ± 0.4 μJy beam−1, implying a hard upper limit on the obscured star formation rate of <0.6 M ⊙ yr−1 (4σ) in a typical low-mass galaxy. The correlation between the infrared excess (IRX) of UV-selected galaxies (L IR/L UV) and the UV-continuum slope is also seen in our ASPECS data and shows consistency with a Calzetti-like relation at >${10}^{9.5}\,{M}_{\odot }$ and an SMC-like relation at lower masses. Using stellar mass and β measurements for z ~ 2 galaxies over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we derive a new empirical relation between β and stellar mass and then use this correlation to show that our IRX–β and IRX–stellar mass relations are consistent with each other. We then use these constraints to express the IRX as a bivariate function of β and stellar mass. Finally, we present updated estimates of star formation rate density determinations at z > 3, leveraging present improvements in the measured IRX and recent probes of ultraluminous far-IR galaxies at z > 2.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.3847/1538-4357/abb830
Publisher statement:© 2020. The American Astronomical Society. All rights reserved.
Date accepted:30 August 2020
Date deposited:05 November 2020
Date of first online publication:19 October 2020
Date first made open access:05 November 2020

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