Cold Dust and Low [OIII]/[CII] Ratios: an Evolved Star-forming Population at Redshift 7

作     者：Algera, Hiddo S.B. Inami, Hanae Sommovigo, Laura Fudamoto, Yoshinobu Schneider, Raffaella Graziani, Luca Dayal, Pratika Bouwens, Rychard Aravena, Manuel da Cunha, Elisabete Ferrara, Andrea Hygate, Alexander P.S. van Leeuwen, Ivana De Looze, Ilse Palla, Marco Pallottini, Andrea Smit, Renske Stefanon, Mauro Topping, Michael van der Werf, Paul P. 

作者机构：Hiroshima Astrophysical Science Center Hiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima739-8526 Japan National Astronomical Observatory of Japan 2-21-1 Osawa Tokyo Mitaka Japan Scuola Normale Superiore Piazza dei Cavalieri 7 PisaI-56126 Italy Waseda Research Institute for Science and Engineering Faculty of Science and Engineering Waseda University 3-4-1 Okubo Shinjuku Tokyo169-8555 Japan Dipartimento di Fisica Sapienza Universita di Roma Piazzale Aldo Moro 5 RomaI-00185 Italy INAF/Osservatorio Astronomico di Roma via Frascati 33 Monte Porzio Catone RomaI-00078 Italy Kapteyn Astronomical Institute University of Groningen P.O. Box 800 Groningen9700 AV Netherlands Leiden Observatory Leiden University LeidenNL-2300 RA Netherlands Departamento de Astronomia Universidad de Chile Camino del Observatorio 1515 Las Condes Santiago7591245 Chile International Centre for Radio Astronomy Research University of Western Australia 35 Stirling Hwy CrawleyWA266009 Australia  Australia Sterrenkundig Observatorium Ghent University Krijgslaan 281 - S9 Gent9000 Belgium Dept. of Physics & Astronomy University College London Gower Street LondonWC1E 6BT United Kingdom INAF Osservatorio Astronomico di Trieste Via G.B. Tiepolo 11 Trieste34131 Italy Dipartimento di Fisica Sezione di Astronomia Universitá di Trieste Via G.B. Tiepolo 11 Trieste34131 Italy Astrophysics Research Institute Liverpool John Moores University 146 Brownlow Hill LiverpoolL3 5RF United Kingdom Departament d’Astronomia i Astrofìsica Universitat de València C. Dr. Moliner 50 Burjassot ValènciaE-46100 Spain  Spain Steward Observatory University of Arizona 933 N Cherry Ave TucsonAZ85721 United States 

出 版 物：《arXiv》 (arXiv)

年 卷 期：2023年

核心收录：

主　　题：Dust 

摘      要：We present new ALMA Band 8 (rest-frame 90 μm) observations of three massive (M★ ≈ 1010 Mo) galaxies at z ≈ 7 previously detected in [CII]158 μm and underlying dust continuum emission in the Reionization Era Bright Emission Line Survey (REBELS). We detect the dust continuum emission of two of our targets in Band 8 (REBELS-25 and REBELS-38), while REBELS-12 remains undetected. Through modified blackbody fitting we determine cold dust temperatures (Tdust ≈ 30−35 K) in both of the dual-band detected targets, given a fiducial model of optically thin emission with β = 2.0. Their dust temperatures are lower than most z ∼ 7 galaxies in the literature, and consequently their dust masses are higher (Mdust ≈ 108 Mo). Nevertheless, these large dust masses are still consistent with predictions from models of dust production in the early Universe. In addition, we target and detect [OIII]88 μm emission in both REBELS-12 and REBELS-25, and find L[OIII]/L[CII]ratios of approximately unity, low compared to the L[OIII]/L[CII] 2 − 10 observed in the known z 6 population thus far. We argue the lower line ratios are due to a comparatively weaker ionizing radiation field resulting from the less starbursty nature of our targets. This low burstiness supports the cold dust temperatures and below average [OIII]λλ4959, 5007 + Hβ equivalent widths of REBELS-25 and REBELS-38, compared to the known high-redshift population. Overall, this provides evidence for the existence of a massive, dust-rich galaxy population at z ≈ 7 which has previously experienced vigorous star formation, but is currently forming stars in a steady, as opposed to bursty, manner. Copyright © 2023, The Authors. All rights reserved.