The VIMOS Public Extragalactic Redshift Survey (VIPERS)

Measuring non-linear galaxy bias at z ~ 0.8 ^⋆

¹ INAF− Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
² Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
³ INFN−Sezione di Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
⁴ INAF−Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone ( RM), Italy
⁵ INAF−Osservatorio Astronomico di Brera, via Brera 28, 20122 Milano, via E. Bianchi 46, 23807 Merate, Italy
⁶ Dipartimento di Fisica e Astronomia − Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁷ INFN−Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁸ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁹ INAF−Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
¹⁰ INFN−Istituto Nazionale di Fisica Nucleare, via Valerio 2, 34127 Trieste, Italy
¹¹ Dipartimento di Fisica, Università di Milano-Bicocca, P.zza della Scienza 3, 20126 Milano, Italy
¹² Centre de Physique Théorique, UMR 6207 CNRS-Université de Provence, Case 907, 13288 Marseille, France
¹³ Astronomical Observatory of the Jagiellonian University, Orla 171, 30-001 Cracow, Poland
¹⁴ National Centre for Nuclear Research, ul. Hoza 69, 00-681 Warszawa, Poland
¹⁵ INAF−Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy
¹⁶ Canada-France-Hawaii Telescope, 65–1238 Mamalahoa Highway, Kamuela, HI 96743, USA
¹⁷ INAF− Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via Bassini 15, 20133 Milano, Italy
¹⁸ Laboratoire Lagrange, UMR 7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
¹⁹ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 10617 Taipei, Taiwan
²⁰ Institute of Physics, Jan Kochanowski University, ul. Swietokrzyska 15, 25-406 Kielce, Poland
²¹ Department of Particleand Astrophysical Science, Nagoya University, Furo-cho, Chikusa-ku, 464-8602 Nagoya, Japan
²² Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
²³ Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Burnaby Road, Portsmouth, PO1 3FX, UK
²⁴ INAF−Istituto di Astrofisica Spaziale e Fisica Cosmica Bologna, via Gobetti 101, 40129 Bologna, Italy
²⁵ INAF−Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
²⁶ SUPA− Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
²⁷ Università degli Studi di Milano, via G. Celoria 16, 20130 Milano, Italy
²⁸ Department of Astronomy, University of California, Berkeley, CA 94720, USA

Received: 22 June 2016
Accepted: 12 April 2016

Abstract

Aims. We use the first release of the VImos Public Extragalactic Redshift Survey of galaxies (VIPERS) of ~50 000 objects to measure the biasing relation between galaxies and mass in the redshift range z = [ 0.5,1.1 ].

Methods. We estimate the 1-point distribution function [PDF] of VIPERS galaxies from counts in cells and, assuming a model for the mass PDF, we infer their mean bias relation. The reconstruction of the bias relation is performed through a novel method that accounts for Poisson noise, redshift distortions, inhomogeneous sky coverage. and other selection effects. With this procedure we constrain galaxy bias and its deviations from linearity down to scales as small as 4 h^-1 Mpc and out to z = 1.1.

Results. We detect small (up to 2%) but statistically significant (up to 3σ) deviations from linear bias. The mean biasing function is close to linear in regions above the mean density. The mean slope of the biasing relation is a proxy to the linear bias parameter. This slope increases with luminosity, which is in agreement with results of previous analyses. We detect a strong bias evolution only for z> 0.9, which is in agreement with some, but not all, previous studies. We also detect a significant increase of the bias with the scale, from 4 to 8 h^-1 Mpc , now seen for the first time out to z = 1. The amplitude of non-linearity depends on redshift, luminosity, and scale, but no clear trend is detected. Owing to the large cosmic volume probed by VIPERS, we find that the mismatch between the previous estimates of bias at z ~ 1 from zCOSMOS and VVDS-Deep galaxy samples is fully accounted for by cosmic variance.

Conclusions. The results of our work confirm the importance of going beyond the over-simplistic linear bias hypothesis showing that non-linearities can be accurately measured through the applications of the appropriate statistical tools to existing datasets like VIPERS.