Multiple star-forming episodes of intermediate-redshift galaxies

¹ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
² Canada-France-Hawaii Telescope, 65-1238 Mamalahoa Highway, Kamuela, HI 96743, USA
³ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
⁴ Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, CNRS, UPS, CNES, Toulouse, France
⁵ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218 Hawthorn, 3122 VIC, Australia
⁶ Universidade Federal do Rio de Janeiro, Observatório do Valongo, Ladeira do Pedro Antônio, 43, Saúde CEP 20080-090 Rio de Janeiro, RJ, Brazil
⁷ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁸ Univ. Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astro-physique de Lyon (CRAL) UMR5574, F-69230 Saint-Genis-Laval, France

^⋆ Corresponding author: cmunoz@aip.de

Received: 17 April 2025
Accepted: 18 August 2025

Abstract

In this work, we derive and analyse the star formation histories of 393 intermediate-redshift (0.1 ≤ z ≤ 0.9) galaxies with stellar masses between ∼10⁸–10¹² M_⊙. We focus on galaxies located in the CANDELS/GOOD-S and CANDELS/COSMOS fields that have been observed with different surveys using MUSE. We probe a cosmic time of approximately 6 billion years (Gyr) and a range of environments, from field (low-density systems) to rich groups (high-density systems). We find that the galaxies’ stellar mean ages, metallicities, and star formation rates (SFRs) follow similar trends to galaxies as those characterising the nearby Universe. We modelled the derived SFRs, quantifying and characterising the number of star-forming episodes (SFEs). We found that more than 85% of the galaxies have more than one event of star formation, typically described with an exponentially decaying SFR and subsequent Gaussian-like episode(s) of star formation. We also observe that massive galaxies have fewer SFEs than low-mass systems and that they form their stellar mass and reach quiescence faster than lower mass galaxies. Moreover, the history of mass assembly for the most massive galaxies in the sample can be described with only one episode of star formation in the early Universe, which we detected as an exponential decrease that was longer in duration than subsequent SF events. This early event has typically been completed by z ∼ 3 and it accounts for a high fraction of the total stellar mass, from ∼40% for low-mass galaxies to more than 50% for higher-mass galaxies. We also analysed the dependence of stellar population parameters with the various environments probed by the sample, finding no significant correlations between different group environments; however, our field galaxies are generally distinct from group galaxies in terms of the mass, metallicity, stellar ages, and formation timescales. We discuss possible biases in the sample selection and examine how representative our galaxies are of the overall galaxy population at the targeted redshifts.