Are Ly{\alpha} emitters segregated in protoclusters regions?

TL;DR

This study investigates how radiative transfer effects influence the spatial distribution and clustering of Lyα emitters in high-density protocluster regions at high redshift, using semi-analytic galaxy formation models.

Contribution

It provides new insights into the impact of ISM and IGM radiative transfer effects on LAE clustering and their spatial segregation from Hα emitters in protoclusters.

Findings

LAEs and HAEs occupy similar regions in protoclusters at z=2.2.

Radiative transfer effects cause a 30-50% decline in LAE clustering amplitude at z=2.2 and z=3.0.

At z=5.7, the impact of radiative transfer on clustering is reduced to 10-20%.

Abstract

The presence of neutral hydrogen in the inter-stellar medium (ISM) and inter-galactic medium (IGM) induces radiative transfer (RT) effects on Ly{\alpha} photons which affect the observability of Ly{\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 H{\alpha} emitters (HAEs) around high density regions at high redshift. We find that when a large sample of protoclusters is considered, HAEs showing also Ly{\alpha} emission (HAEs+LAEs) populate the same regions as those that do not display the Ly{\alpha} line at $z=2.2$. We compare against the protocluster USS1558-003, one of the most massive protoclusters located at $z=2.53$. 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 $z=2.2$ and $z=3.0$, 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 $z=5.7$, 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.