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ALMA Characterises 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 Characterises the Dust Temperature of z ~ 5.5 Star-Forming Galaxies. . (Unpublished)

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The infrared spectral energy distributions (SEDs) of main-sequence galaxies in the early universe (z > 4) is currently unconstrained as infrared continuum observations are time consuming and not feasible for large samples. We present Atacama Large Millimetre Array (ALMA) Band 8 observations of four main-sequence galaxies at z ~ 5.5 to study their infrared SED shape in detail. Our continuum data (rest-frame 110μm, close to the peak of infrared emission) allows us to constrain luminosity weighted dust temperatures and total infrared 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 (38±8K) are elevated compared to average local galaxies, however, 5-10K 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 infrared SED at the peak to be more optically thin, making hot dust more visible to the external observer. From the 850μm dust continuum, we derive molecular gas masses between 10¹⁰ and 10¹¹ M⊙ and gas fractions (gas over total mass) of 30-80% (gas depletion times of 100-220Myrs). 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:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Faisst, Andreas L.0000-0002-9382-9832
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
Additional Information:© 2020 The Authors. 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'. D.R. acknowledges support from the National Science Foundation under grant numbers AST-1614213 and AST-1910107. D.R. also acknowledges support from the Alexander von Humboldt Foundation through a Humboldt Research Fellowship for Experienced Researchers.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)157567
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:galaxies: high-redshift - (ISM:) dust, extinction - galaxies: ISM
Record Number:CaltechAUTHORS:20200720-071439633
Persistent URL:
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:20 Jul 2020 16:23

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