The ALMA-ALPINE [CII] survey: Kennicutt-Schmidt relation in four massive main-sequence galaxies at z  ∼  4.5

¹ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
² Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
e-mail: matthieu.bethermin@astro.unistra.fr
³ Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁴ Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso, Chile
⁵ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁶ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁷ IPAC, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA, 91125 USA
⁸ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH UK
⁹ Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8526 Japan
¹⁰ National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo, Japan
¹¹ ARAID Foundation, Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC, Plaza San Juan 1, 44001 Teruel, Spain
¹² Departamento de Astronomía, Universidad de La Serena, Av. Juan Cisternas 1200 Norte, La Serena, 1720236 Chile
¹³ Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica, Chile
¹⁴ Astronomy Department, University of Wisconsin, Madison, WI, USA
¹⁵ Institut d’Astrophysique de Paris, CNRS and Sorbonne Université, UMR 7095, 98 bis Boulevard Arago, 75014 Paris, France
¹⁶ Scuola Normale Superiore, Piazza dei Cavalieri 7, 50126 Pisa, Italy
¹⁷ Astronomy Department, University of Massachusetts, Amherst, MA, 01003 USA
¹⁸ University of Bologna – Department of Physics and Astronomy “Augusto Righi” (DIFA), Via Gobetti 93/2, 40129 Bologna, Italy
¹⁹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
²⁰ Space Telescope Science Institute, Baltimore, MD, 21218 USA
²¹ Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY, 10010 USA
²² Department of Physics and Astronomy, University of California Davis, One Shields Avenue, Davis, CA, 95616 USA
²³ Cosmic Dawn Center (DAWN), Jagtvej 128, 2200 Copenhagen N, Denmark
²⁴ DTU-Space, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
²⁵ Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen N, Denmark
²⁶ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
²⁷ Department of Astronomy, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL, 32611 USA
²⁸ National Centre for Nuclear Research, ul. Pasteura 7, 02-093 Warsaw, Poland
²⁹ Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522 Japan
³⁰ Dipartimento di Fisica e Astronomia, Universitá degli Studi di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
³¹ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³² Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland
³³ Gemini Observatory, NSF’s NOIRLab, 670 N. A’ohoku Place, Hilo, Hawai’i, 96720 USA

Received: 29 September 2023
Accepted: 13 November 2023

Abstract

Aims. The Kennicutt-Schmidt (KS) relation between the gas and the star formation rate (SFR) surface density (Σ_gas − Σ_SFR) is essential to understand star formation processes in galaxies. To date, it has been measured up to z ∼ 2.5 in main-sequence galaxies. In this Letter our aim is to put constraints at z ∼ 4.5 using a sample of four massive main-sequence galaxies observed by ALMA at high resolution.

Methods. We obtained ∼0.3″-resolution [CII] and continuum maps of our objects, which we then converted into gas and obscured SFR surface density maps. In addition, we produced unobscured SFR surface density maps by convolving Hubble ancillary data in the rest-frame UV. We then derived the average Σ_SFR in various Σ_gas bins, and estimated the uncertainties using a Monte Carlo sampling.

Results. Our galaxy sample follows the KS relation measured in main-sequence galaxies at lower redshift, and is slightly lower than the predictions from simulations. Our data points probe the high end both in terms of Σ_gas and Σ_SFR, and gas depletion timescales (285–843 Myr) remain similar to z ∼ 2 objects. However, three of our objects are clearly morphologically disturbed, and we could have expected shorter gas depletion timescales (≲100 Myr) similar to merger-driven starbursts at lower redshifts. This suggests that the mechanisms triggering starbursts at high redshift may be different than in the low- and intermediate-z Universe.