Less and more IGM-transmitted galaxies from z ∼ 2.7 to z ∼ 6 from VANDELS and VUDS^⋆,⋆⋆

¹ European Southern Observatory, Av. Alonso de Córdova 3107, Vitacura, Santiago, Chile
e-mail: rthomas@eso.org
² INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy
³ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁴ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
⁵ INAF – Osservatorio Astrofisico di Arcetri, largo E. Fermi 5, 50125 Firenze, Italy
⁶ INAF-Astronomical Observatory, Via G.B. Tiepolo 11, 34143 Trieste, Italy
⁷ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy
⁸ INAF IASF-Milano, Via A.Corti 12, 20133 Milano, Italy
⁹ University of Bologna – Department of Physics and Astronomy, Via Gobetti 93/2, 40129 Bologna, Italy
¹⁰ Instituto de Investigación Multidisciplinar en Ciencia y Tecnología, Universidad de La Serena, Raúl Bitrán 1305, La Serena, Chile
¹¹ Departamento de Astronomía, Universidad de La Serena, Av. Juan Cisternas 1200 Norte, La Serena, Chile
¹² AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
¹³ Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK
¹⁴ Cosmic DAWN Center, Vibenshuset, Lyngbyvej 2, 2100 Copenhagen, Denmark
¹⁵ Niels Bohr Institute, Copenhagen University, Lyngbyvej 2, 2100 Copenhagen O, Denmark
¹⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁸ Department of Physics, University of California, Davis, One Shields Ave., Davis, CA 95616, USA
¹⁹ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland

Received: 18 May 2020
Accepted: 18 February 2021

Abstract

Aims. Our aim is to analyze the variance of the intergalactic medium (IGM) transmission by studying this parameter in the rest-frame UV spectra of a large sample of high-redshift galaxies.

Methods. We made use of the VIMOS Ultra Deep Survey and the VANDELS public survey to gain insight into the far UV spectrum of 2.7 < z < 6 galaxies. Using the SPARTAN fitting software, we estimated the IGM toward individual galaxies and then divided them into two sub-samples characterized by a transmission above or below the theoretical prescription. We created average spectra of combined VUDS and VANDELS data for each set of galaxies in seven redshift bins.

Results. The resulting spectra clearly exhibit the variance of the IGM transmission that can be seen directly from high-redshift galaxy observations. Computing the optical depth based on the IGM transmission, we find an excellent agreement with results for quasi-stellar objects. In addition, our measurements appear to suggest that there is a large dispersion of redshift where a complete Gunn-Peterson Trough occurs, depending on the line of sight.