The ALMA-CRISTAL survey: Gas, dust, and stars in star-forming galaxies when the Universe was ∼1 Gyr old

I. Survey overview and case studies

¹ Departamento de Astronomía, Universidad de Concepción, Barrio Universitario, Concepción, Chile
² Millenium Nucleus for Galaxies (MINGAL), Concepción, Chile
³ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
⁴ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
⁵ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441 Santiago 8370191, Chile
⁶ Sterrenkundig Observatorium, Ghent University, Krijgslaan 281 – S9, B9000 Ghent, Belgium
⁷ Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843-4242, USA
⁸ Faculty of Engineering, Hokkai-Gakuen University, Toyohira-ku, Sapporo 062-8605, Japan
⁹ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁰ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
¹¹ Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA
¹² Leiden Observatory, Leiden University, NL-2300 RA Leiden, The Netherlands
¹³ Chemistry Department, Sapienza University of Rome, P.le A. Moro, 00185 Rome, Italy
¹⁴ International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, M468, 35 Stirling Highway, Crawley, WA 6009, Australia
¹⁵ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
¹⁶ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Canberra, ACT, Australia
¹⁷ Institute of Astrophysics, Foundation for Research and Technology – Hellas (FORTH), Voutes, 70013 Heraklion, Greece
¹⁸ School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
¹⁹ Scuola Normale Superiore, Piazza dei Cavalieri 7, 50126 Pisa, Italy
²⁰ Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), Mitaka, Tokyo 181-8588, Japan
²¹ Purple Mountain Observatory, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210023, China
²² Department for Astrophysical & Planetary Science, University of Colorado, Boulder, CO 80309, USA
²³ Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
²⁴ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany
²⁵ Dipartimento di Fisica e Astronomia “Augusto Righi”, Alma Mater Studiorum, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
²⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
²⁷ Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
²⁸ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
²⁹ School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
³⁰ Dept. Fisica Teorica y del Cosmos, Universidad de Granada, Granada, Spain
³¹ Department of Astronomy, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL 32611, USA
³² Cosmic Dawn Center at the Niels Bohr Institute, University of Copenhagen and DTU-Space, Technical University of Denmark, Copenhagen, Denmark
³³ Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22903, USA
³⁴ Las Campanas Observatory, Carnegie Institution of Washington, Raúl Bitrán 1200, La Serena, Chile
³⁵ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Manchester M13 9PL, UK

^⋆ Corresponding author: rhc@astro-udec.cl

Received: 24 January 2025
Accepted: 1 April 2025

Abstract

We present the ALMA-CRISTAL survey, an ALMA Cycle 8 Large Program designed to investigate the physical properties of star-forming galaxies at 4 ≲ z ≲ 6 through spatially resolved, multiwavelength observations. This survey targets 19 star-forming main-sequence galaxies selected from the ALPINE survey, using ALMA Band 7 observations to study [C II] 158 μm line emission and dust continuum, complemented by JWST/NIRCam and HST imaging to map stellar and UV emission. The CRISTAL sample expanded to 39 after including newly detected galaxies in the CRISTAL fields, archival data, and pilot study targets. The resulting dataset provides a detailed view of gas, dust, and stellar structures on kiloparsec scales at the end of the era of reionization. The survey reveals diverse morphologies and kinematics, including rotating disks, merging systems, [C II] emission tails from potential interactions, and clumpy star formation. Notably, the [C II] emission in many cases extends beyond the stellar light seen in HST and JWST imaging. Scientific highlights include CRISTAL-10, exhibiting an extreme [C II] deficit similar to Arp 220, and CRISTAL-13, where feedback from young star-forming clumps likely causes an offset between the stellar clumps and the peaks of [C II] emission. CRISTAL galaxies exhibit global [C II]/FIR ratios that decrease with increasing FIR luminosity, similar to trends seen in local galaxies but shifted to higher luminosities, likely due to their higher molecular gas content. CRISTAL galaxies also span a previously unexplored range of global FIR surface brightness at high-redshift, showing that high-redshift galaxies can have elevated [C II]/FIR ratios. These elevated ratios are likely influenced by factors such as lower-metallicity gas, the presence of significant extraplanar gas, and contributions from shock-excited gas.