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ALMA characterizes the dust temperature of z ∼ 5.5 star-forming galaxies

Faisst, Andreas L. and Fudamoto, Yoshinobu and Oesch, Pascal A. and Scoville, Nick and Riechers, Dominik A. and Pavesi, Riccardo and Capak, Peter (2020) ALMA characterizes the dust temperature of z ∼ 5.5 star-forming galaxies. Monthly Notices of the Royal Astronomical Society, 498 (3). pp. 4192-4204. ISSN 0035-8711.

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The infrared (IR) spectral energy distributions (SEDs) of main-sequence galaxies in the early Universe (z > 4) is currently unconstrained as IR continuum observations are time-consuming and not feasible for large samples. We present Atacama Large Millimetre Array Band 8 observations of four main-sequence galaxies at z ∼ 5.5 to study their IR SED shape in detail. Our continuum data (rest-frame 110 μm⁠, close to the peak of IR emission) allows us to constrain luminosity-weighted dust temperatures and total IR luminosities. With data at longer wavelengths, we measure for the first time the emissivity index at these redshifts to provide more robust estimates of molecular gas masses based on dust continuum. The Band 8 observations of three out of four galaxies can only be reconciled with optically thin emission redward of rest-frame 100μm⁠. The derived dust peak temperatures at z ∼ 5.5 (⁠30−43K⁠) are elevated compared to average local galaxies, however, ∼10K below what would be predicted from an extrapolation of the trend at z < 4. This behaviour can be explained by decreasing dust abundance (or density) towards high redshifts, which would cause the IR SED at the peak to be more optically thin, making hot dust more visible to the external observer. From the 850-μm dust continuum, we derive molecular gas masses between 10¹⁰ and 10¹¹M⊙ and gas fractions (gas over total mass) of 30−80 per cent (gas depletion times of 100−220 Myr⁠). All in all, our results provide a first measured benchmark SED to interpret future millimetre observations of normal, main-sequence galaxies in the early Universe.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemALMA Science Archive
Faisst, Andreas L.0000-0002-9382-9832
Fudamoto, Yoshinobu0000-0001-7440-8832
Oesch, Pascal A.0000-0001-5851-6649
Scoville, Nick0000-0002-0438-3323
Riechers, Dominik A.0000-0001-9585-1462
Pavesi, Riccardo0000-0002-2263-646X
Capak, Peter0000-0003-3578-6843
Alternate Title:ALMA Characterises the Dust Temperature of z ~ 5.5 Star-Forming Galaxies
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Received: 12 May 2020; Revision received: 18 July 2020; Accepted: 09 August 2020; Published: 22 August 2020. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2018.1.00348.S, ADS/JAO.ALMA#2017.1.00428.L, ADS/JAO.ALMA#2015.1.00388.S, ADS/JAO.ALMA#2015.1.00928.S, ADS/JAO.ALMA#2012.1.00523.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work was supported by the Swiss National Science Foundation through the SNSF Professorship grant 157567 ‘Galaxy Build-up at Cosmic Dawn’. DAR acknowledges support from the National Science Foundation under grant numbers AST-1614213 and AST-1910107. DAR also acknowledges support from the Alexander von Humboldt Foundation through a Humboldt Research Fellowship for Experienced Researchers. Finally, we thank the referee for the very useful comments that improved this manuscript. Data Availability: The data underlying this paper were accessed from the ALMA science archive ( The program identifiers are ADS/JAO.ALMA#2018.1.00348.S, ADS/JAO.ALMA#2017.1.00428.L, ADS/JAO.ALMA#2015.1.00388.S, ADS/JAO.ALMA#2015.1.00928.S, and ADS/JAO.ALMA#2012.1.00523.S. The individual and stacked best-fitting IR SEDs (Fig. 3) are available in the online version or on request.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)157567
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:dust, extinction – galaxies: high-redshift – galaxies: ISM
Issue or Number:3
Record Number:CaltechAUTHORS:20200720-071439633
Persistent URL:
Official Citation:Andreas L Faisst, Yoshinobu Fudamoto, Pascal A Oesch, Nick Scoville, Dominik A Riechers, Riccardo Pavesi, Peter Capak, ALMA characterizes the dust temperature of z ∼ 5.5 star-forming galaxies, Monthly Notices of the Royal Astronomical Society, Volume 498, Issue 3, November 2020, Pages 4192–4204,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104435
Deposited By: Tony Diaz
Deposited On:20 Jul 2020 16:23
Last Modified:05 Jan 2021 00:17

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