The VIMOS Public Extragalactic Redshift Survey (VIPERS)

The distinct build-up of dense and normal massive passive galaxies^⋆

¹ INAF–Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via Bassini 15, 20133 Milano, Italy
e-mail: adriana@lambrate.inaf.it
² INAF–Osservatorio Astronomico di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
³ Institute of Physics, Jan Kochanowski University, ul. Swietokrzyska 15, 25-406 Kielce, Poland
⁴ INAF–Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
⁵ INAF–Osservatorio Astronomico di Brera, via Brera 28, 20122 Milano, via E. Bianchi 46, 23807 Merate, Italy
⁶ Università degli Studi di Milano, via G. Celoria 16, 20133 Milano, Italy
⁷ Aix-Marseille Univ, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, 13013 Marseille, France
⁸ INAF–Osservatorio Astrofisico di Torino, 10025 Pino Torinese, Italy
⁹ Laboratoire Lagrange, UMR7293, Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
¹⁰ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
¹¹ National Centre for Nuclear Research, ul. Hoza 69, 00-681 Warszawa, Poland
¹² INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
¹³ Department of Astronomy & Physics, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada
¹⁴ Aix-Marseille Université, Jardin du Pharo, 58 bd Charles Livon, 13284 Marseille Cedex 7, France
¹⁵ IRAP, 9 Av. du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹⁶ Astronomical Observatory of the Jagiellonian University, Orla 171, 30-001 Cracow, Poland
¹⁷ School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
¹⁸ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica Bologna, via Gobetti 101, 40129 Bologna, Italy
¹⁹ INAF – Istituto di Radioastronomia, via Gobetti 101, 40129, Bologna, Italy
²⁰ Aix-Marseille Univ, Univ Toulon, CNRS, CPT, 13288 Marseille, France
²¹ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
²² INFN, Sezione di Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
²³ INAF–Osservatorio Astronomico di Roma, via Frascati33, 00040 Monte Porzio Catone (RM), Italy
²⁴ Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland
²⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

Received: 22 November 2016
Accepted: 19 May 2017

Abstract

We have used the final data from the VIPERS redshift survey to extract an unparalleled sample of more than 2000 massive ℳ≥10¹¹ M_⊙ passive galaxies (MPGs) at redshift 0.5≤z≤1.0, based on their NUVrK colours. This has enabled us to investigate how the population of these objects was built up over cosmic time. We find that the evolution of the number density depends on the galaxy mean surface stellar mass density, Σ. In particular, dense (Σ≥2000 M_⊙ pc^-2) MPGs show a constant comoving number density over this redshift range, whilst this increases by a factor of approximately four for the least dense objects, defined as having Σ < 1000 M_⊙ pc^-2. We estimated stellar ages for the MPG population both fitting the spectral energy distribution (SED) and through the D4000_n index, obtaining results in good agreement. Our findings are consistent with passive ageing of the stellar content of dense MPGs. We show that at any redshift the less dense MPGs are younger than dense ones and that their stellar populations evolve at a slower rate than predicted by passive evolution. This points to a scenario in which the overall population of MPGs was built up over the cosmic time by continuous addition of less dense galaxies: on top of an initial population of dense objects that passively evolves, new, larger, and younger MPGs continuously join the population at later epochs. Finally, we demonstrate that the observed increase in the number density of MPGs is totally accounted for by the observed decrease in the number density of correspondingly massive star forming galaxies (i.e. all the non-passive ℳ≥10¹¹ M_⊙ objects). Such systems observed at z ≃ 1 in VIPERS, therefore, represent the most plausible progenitors of the subsequent emerging class of larger MPGs.