The VIMOS Ultra Deep Survey: The reversal of the star-formation rate − density relation at 2 < z < 5

¹ Aix-Marseille Univ, CNRS, CNES, Laboratoire d’Astrophysique de Marseille, Marseille, France
e-mail: brian.lemaux@noirlab.edu
² Department of Physics and Astronomy, University of California, One Shields Ave., Davis, CA 95616, USA
³ , 670 N. A’ohoku Place, Hilo, HI 96720, USA
⁴ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁶ UCO/Lick Observatory, Department of Astronomy & Astrophysics, UCSC, 1156 High Street, Santa Cruz, CA 95064, USA
⁷ Instituto de Investigacíon Multidisciplinar en Ciencia y Tecnología, Universidad de La Serena, Raul Bitrán 1305, La Serena, Chile
⁸ Departamento de Física y Astronomía, Universidad de La Serena, Av. Juan Cisternas 1200 Norte, La Serena, Chile
⁹ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio, 3, 35122 Padova, Italy
¹⁰ INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹¹ University of Hawai’i, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
¹² INAF–IASF, Via Bassini 15, 20133 Milano, Italy
¹³ INAF–Osservatorio Astronomico di Roma, Via di Frascati 33, 00040 Monte Porzio Catone, Italy
¹⁴ Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
¹⁵ Astronomy Department, University of Massachusetts, Amherst, MA 01003, USA
¹⁶ Leiden Observatory, Leiden University, PO Box 9513 2300 RA, Leiden, The Netherlands
¹⁷ Geneva Observatory, University of Geneva, Ch. des Maillettes 51, 1290 Versoix, Switzerland
¹⁸ CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
¹⁹ School of Astronomy and Space Sciences, University of Science and Technology of China, Hefei 230026, PR China
²⁰ European Southern Observatory, Av. Alonso de Córdova 3107, Vitacura, Santiago, Chile

Received: 5 September 2020
Accepted: 28 February 2022

Abstract

Utilizing spectroscopic observations taken for the VIMOS Ultra-Deep Survey (VUDS), new observations from Keck/DEIMOS, and publicly available observations of large samples of star-forming galaxies, we report here on the relationship between the star-formation rate (SFR) and the local environment (δ_gal) of galaxies in the early universe (2 < z < 5). Unlike what is observed at lower redshifts (z ≲ 2), we observe a definite, nearly monotonic increase in the average SFR with increasing galaxy overdensity over more than an order of magnitude in δ_gal. The robustness of this trend is quantified by accounting for both uncertainties in our measurements and galaxy populations that are either underrepresented or not present in our sample (e.g., extremely dusty star-forming and quiescent galaxies), and we find that the trend remains significant under all circumstances. This trend appears to be primarily driven by the fractional increase of galaxies in high-density environments that are more massive in their stellar content and are forming stars at a higher rate than their less massive counterparts. We find that, even after stellar mass effects are accounted for, there remains a weak but significant SFR–δ_gal trend in our sample implying that additional environmentally related processes are helping to drive this trend. We also find clear evidence that the average SFR of galaxies in the densest environments increases with increasing redshift. These results lend themselves to a picture in which massive gas-rich galaxies coalesce into proto-cluster environments at z ≳ 3, interact with other galaxies or with a forming large-scale medium, subsequently using or losing most of their gas in the process, and begin to seed the nascent red sequence that is present in clusters at slightly lower redshifts.