The ALMA-CRISTAL survey

Widespread dust-obscured star formation in typical star-forming galaxies at z = 4–6

¹ Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo Tokyo 113-0033, Japan
² National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka Tokyo 181-8588, Japan
³ Faculty of Engineering, Hokkai-Gakuen University, Toyohira-ku, Sapporo 062-8605, Japan
⁴ Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), Mitaka Tokyo 181-8588, Japan
⁵ Departamento de Astronomía, Universidad de Concepción, Barrio Universitario, Concepción, Chile
⁶ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441 Santiago, Chile
⁷ Sterrenkundig Observatorium, Ghent University Krijgslaan 281 – S9, B-9000 Ghent, Belgium
⁸ Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁹ Max-Planck-Institut für Extraterrestrische Physik (MPE), Giessenbachstr., 85748 Garching, Germany
¹⁰ Las Campanas Observatory, Carnegie Institution of Washington, Casilla 601, La Serena, Chile
¹¹ Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX, USA
¹² Leiden Observatory, Leiden University, NL-2300 RA Leiden, Netherlands
¹³ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
¹⁴ Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22903, USA
¹⁵ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Manchester M13 9PL, UK
¹⁶ European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
¹⁷ Centre for Astrophysics and Supercomputing, Swinburne Univ. of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
¹⁸ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
¹⁹ International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Hwy., Crawley, WA 6009, Australia
²⁰ Institute of Astrophysics, Foundation for Research and Technology-Hellas (FORTH), Heraklion 70013, Greece
²¹ Chinese Academy of Sciences South America Center for Astronomy (CASSACA), National Astronomical Observatories, CAS, Beijing 100101, PR China
²² Scuola Normale Superiore, Piazza dei Cavalieri 7, I-50126 Pisa, Italy
²³ International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, M468, 35 Stirling Highway, Crawley, WA 6009, Australia
²⁴ Dept. Fisica Teorica y del Cosmos, Universidad de Granada, Granada, Spain
²⁵ Instituto Universitario Carlos I de Física Teórica y Computacional, Universidad de Granada, E-18071 Granada, Spain
²⁶ Max-Planck Institute for Astrophysics, Karl Schwarzschildstrasse 1, 85748 Garching, Germany
²⁷ INAF – OAS, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
²⁸ Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Avenue, Cambridge CB3 0HE, UK
²⁹ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
³⁰ Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park, Maryland 20742, USA

Received: 29 November 2023
Accepted: 17 June 2024

Abstract

We present the morphological parameters and global properties of dust-obscured star formation in typical star-forming galaxies at z = 4–6. Among 26 galaxies composed of 20 galaxies observed by the Cycle-8 ALMA Large Program, CRISTAL, and 6 galaxies from archival data, we individually detect rest-frame 158 μm dust continuum emission from 19 galaxies, 9 of which are reported for the first time. The derived far-infrared luminosities are in the range log₁₀L_IR [L_⊙] = 10.9 − 12.4, an order of magnitude lower than previously detected massive dusty star-forming galaxies (DSFGs). We find the average relationship between the fraction of dust-obscured star formation (f_obs) and the stellar mass to be consistent with previous results at z = 4–6 in a mass range of log₁₀M_* [M_⊙]∼9.5 − 11.0 and to show potential evolution from z = 6 − 9. The individual f_obs exhibits significant diversity, and we find a potential correlation with the spatial offset between the dust and UV continuum, suggesting that inhomogeneous dust reddening may cause the source-to-source scatter in f_obs. The effective radii of the dust emission are on average ∼1.5 kpc and are about two times more extended than those seen in rest-frame UV. The infrared surface densities of these galaxies (Σ_IR ∼ 2.0 × 10¹⁰ L_⊙ kpc⁻²) are one order of magnitude lower than those of DSFGs that host compact central starbursts. On the basis of the comparable contribution of dust-obscured and dust-unobscured star formation along with their similar spatial extent, we suggest that typical star-forming galaxies at z = 4 − 6 form stars throughout the entirety of their disks.