The environments of high redshift radio galaxies and quasars: probes of protoclusters

TL;DR

This study uses semi-analytical modeling to explore the environments of high-redshift radio galaxies and quasars, revealing their connection to protoclusters and how baryonic physics influences galaxy properties in dense regions.

Contribution

It provides new insights into the properties of protoclusters associated with radio galaxies and quasars, including scaling relations and the impact of baryonic physics on galaxy clustering.

Findings

Radio galaxies are hosted by more massive haloes than quasars.

Protocluster overdensities correlate with descendant halo masses.

Spectral resolution can map protocluster structures effectively.

Abstract

We use the GALFORM semi-analytical model to study high density regions traced by radio galaxies and quasars at high redshifts. We explore the impact that baryonic physics has upon the properties of galaxies in these environments. Star-forming emission-line galaxies (Ly{\alpha} and H{\alpha} emitters) are used to probe the environments at high redshifts. Radio galaxies are predicted to be hosted by more massive haloes than quasars, and this is imprinted on the amplitude of galaxy overdensities and cross-correlation functions. We find that Ly{\alpha} radiative transfer and AGN feedback indirectly affect the clustering on small scales and also the stellar masses, star- formation rates and gas metallicities of galaxies in dense environments. We also investigate the relation between protoclusters associated with radio galaxies and quasars, and their present- day cluster descendants. The progenitors of massive clusters associated with radio galaxies and quasars allow us to determine an average protocluster size in a simple way. Overdensities within the protoclusters are found to correlate with the halo descendant masses. We present scaling relations that can be applied to observational data. By computing projection effects due to the wavelength resolution of modern spectrographs and narrow-band filters we show that the former have enough spectral resolution to map the structure of protoclusters, whereas the latter can be used to measure the clustering around radio galaxies and quasars over larger scales to determine the mass of dark matter haloes hosting them.