The less and the more IGM transmitted galaxies from z~2.7 to z~6 from VANDELS and VUDS

TL;DR

This study analyzes the variance in intergalactic medium transmission at high redshifts (z~2.7 to 6) using galaxy spectra from VUDS and VANDELS, revealing significant transmission variability and agreement with quasar data.

Contribution

It provides the first detailed analysis of IGM transmission variance in galaxy spectra across multiple redshifts, highlighting the dispersion in Gunn-Peterson Trough occurrence.

Findings

IGM transmission variance is observable directly in galaxy spectra.

Excellent agreement with quasar-based optical depth measurements.

Large dispersion in redshift for complete Gunn-Peterson Trough occurrence.

Abstract

Aim. Our aim is to analyse the variance of the Inter-Galactic Medium transmission (IGM) by studying this parameter in the rest-frame UV spectra of a large sample of high redshift galaxies. Method. We make use of the VIMOS Ultra Deep Survey and the VANDELS public survey to have an insight into the far UV spectrum of $2.7<z<6$ galaxies. Using the SPARTAN fitting software, we estimate the IGM towards individual galaxies and then divide them in two sub-samples characterized by a transmission above or below the theoretical prescription. We create 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 QSOs results. In addition, our measurements seem to suggest that there is a large dispersion of redshift where complete Gunn-Peterson Trough happens, depending on the line of sight.