Lightening up Dark Galaxy candidates beyond redshift 3 with MUSE

Theoretical models suggest that each galaxy pass through a 'dark galaxy' phase of formation that involves an epoch when galaxies are gas-rich but inefficient at forming stars. Here, I present the new results published in Marino et al: 2018 on the search for dark galaxies at high redshift (z >3) from the analysis of six MUSE (Multi Unit Spectroscopic Explorer) deep fields. In particular, we take advantage of the quasar-induced fluorescent Lyman emission to detect and study these otherwise invisible objects to our optical telescopes. In addition, contrary to previous studies based on deep narrow-band (NB) imaging, our integral fieldsurvey has several advantages including a nearly uniform sensitivity coverage over a large volume in redshift space as well as full spectral information at each location. Specifically, in Marino et al: 2018, we study the rest-frame equivalent width (EW0) distributions of the Ly sources detected in proximity to the quasars and in control samples. We find a clear correlation between the locations of high EW0 objects and the quasars. This correlation is not seen in other properties such as Ly luminosities or volume over densities, suggesting their possible fluorescent nature. Our main result is the discovery of 8 Ly sources without continuum counterparts and EW0 limits larger than 240A that, so far, are the best and only candidates for dark galaxies at z >3.