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

Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe 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 α and H α 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 α radiative transfer and active galactic nucleus 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.

HST GRISM CONFIRMATION OF TWO z ∼ 2 STRUCTURES FROM THE CLUSTERS AROUND RADIO-LOUD AGN (CARLA) SURVEY

“…Brodwin et al (2013) predicted that this transition redshift should be a function of halo mass, with more massive halos transitioning earlier. This is consistent with the findings of Wylezalek et al (2014) of ã z 3 transition period for clusters around radio-loud active galactic nuclei (RLAGN), which are extreme objects that tend to reside in the most massive dark matter halos (e.g., Mandelbaum et al 2009;Hatch et al 2014;Orsi et al 2016).…”

Quasars as a Tracer of Large-Scale Structures in the Distant Universe

“…This might imply that quasars can be used as an efficient probe of dense environments such as protoclusters at high redshifts. Orsi et al (2016) performed a numerical study of protoclusters associated with radio galaxies and quasars at 2<z<6, and studied their connection to present-day cluster descendants. By finding high-z protoclusters with high-z quasars, the connection can be studied observationally.…”

A Radio-to-mm Census of Star-forming Galaxies in Protocluster 4C23.56 at Z = 2.5: Gas Mass and Its Fraction Revealed with ALMA

“…Radio galaxy 4C23.56 (HAE1) at z= 2.483±0.003 is associated with this protocluster (Roettgering et al 1997). Historically, radio galaxies have been targeted in a search for (proto)clusters since their hosts are the most massive galaxies (Seymour et al 2007) and are expected to be embedded in the most massive halos (e.g., Rocca-Volmerange et al 2004;Orsi et al 2016). Indeed, the method has successfully yielded promising results to find (proto)clusters (e.g., Le Fevre et al 1996;Kurk et al 2000;Best et al 2003;De Breuck et al 2004;Overzier et al 2006;Venemans et al 2007;Hatch et al 2011) and protocluster 4C23.56 is also one of them.…”