Are Ly α emitters segregated in protoclusters regions?

Abstract

The presence of neutral hydrogen in the interstellar medium (ISM) and intergalactic medium (IGM) induces radiative transfer (RT) effects on LyαLyα photons that affect the observability of Lyman alpha emitters (LAEs). We use the GALFORM semi-analytic model of galaxy formation and evolution to analyse how these effects shape the spatial distribution of LAEs with respect to HαHα emitters (HAEs) around high-density regions at high redshift. We find that when a large sample of protoclusters is considered, HAEs showing also LyαLyα emission (HAEs + LAEs) populate the same regions as those that do not display the LyαLyα line at zz = 2.2. We compare against the protocluster USS1558-003, one of the most massive protoclusters located at zz = 2.53. Our results indicate that the strong depletion of HAEs + LAEs present in the high-density regions of USS1558-003 may be due to cosmic variance. We find that at zz = 2.2 and zz = 3.0, RT of the ISM produces a strong decline (30-50 per cent) of the clustering amplitude of HAEs + LAEs with respect to HAEs towards the protoclusters centre. At zz = 5.7, given the early evolutionary state of protoclusters and galaxies, the clustering of HAEs + LAEs has a smaller variation (10-20 per cent) towards the protoclusters centre. Depending on the equivalent width and luminosity criteria of the emission-line galaxy sample, the IGM can have a mild or a null effect on galaxy properties and clustering in high-density regions.