Overdensities of SMGs around WISE-selected, ultraluminous, high-redshift AGNs

Abstract

We investigate extremely luminous dusty galaxies in the environments around WISEselected hot dust obscured galaxies (Hot DOGs) and WISE /radio-selected active galactic nuclei (AGNs) at average redshifts of z = 2.7 and z = 1.7, respectively. Previous observations have detected overdensities of companion submillimetre-selected sources around 10 Hot DOGs and 30 WISE /radio AGNs, with overdensities of ∼ 2 − 3 and ∼ 5 − 6, respectively. We find that the space densities in both samples to be overdense compared to normal star-forming galaxies and submillimetre galaxies (SMGs) in the SCUBA-2 Cosmology Legacy Survey (S2CLS). Both samples of companion sources have consistent mid-IR colours and mid-IR to submm ratios as SMGs. The brighter population around WISE /radio AGNs could be responsible for the higher overdensity reported. We also find the star formation rate density (SFRDs) are higher than the field, but consistent with clusters of dusty galaxies. WISE -selected AGNs appear to be good signposts for protoclusters at high redshift on arcmin scales. The results reported here provide an upper limit to the strength of angular clustering using the two-point correlation function. Monte Carlo simulations show no angular correlation, which could indicate protoclusters on scales larger than the SCUBA-2 1.5 arcmin scale maps.

Cosmic dance at z ~ 3: Detecting the host galaxies of the dual AGN system LBQS 0302–0019 and Jil with HAWK-I+GRAAL

“…Luminous radio-loud AGN at 1.2 < z < 3 have been found to systematically reside in galaxy overdensities on arcminute scales (e.g., Ivison et al 2000;Smail et al 2003;Wylezalek et al 2013;Rigby et al 2014;Malavasi et al 2015;Jones et al 2015;Silva et al 2015). Similar studies for radio-quiet AGN have also revealed galaxy overdensities around them (e.g., Utsumi et al 2010;Capak et al 2011;Morselli et al 2014;Jones et al 2017), although contradictory results have been reported (Kikuta et al 2017;Mazzucchelli et al 2017). Furthermore, halo masses of luminous AGN have been estimated through clustering studies, which either found that they reside in overdensities (e.g., Croom et al 2002;Coil et al 2009) or in normal environments (Coil et al 2007).…”

The Overdense Environments of WISE-Selected, Ultra-Luminous, High-Redshift AGN in the Submillimeter

“…Both sets of companion sources have similar WISE colors, Jones et al (2017). When comparing with the WISE color-color diagram of different galaxy populations in Figure 12 in Wright et al (2010) and Figure 26 in Jarrett et al (2011), the companion sources lie in both the starburst (star-forming) galaxy zone and AGN zone.…”

“…This could be due to differences in redshift and/or radio emission. However, more observations are needed because only 10 targets in each sample have known redshifts, Jones et al (2017).…”

“…It is the excess probability of finding galaxies separated by θ above the probability with a random distribution. The popular estimators described by Landy and Szalay (1993) Jones et al (2017). The red solid curve shows the observed angular two-point correlation function for Weiß et al (2009).…”

“…The two-point angular clustering signal provided an upper limit to the strength of angular clustering (Jones et al, 2017), see Figure 1. Monte Carlo simulations showed no angular correlation, which could indicate protoclusters on scales larger than the SCUBA-2 1.5 arcmin scale maps.…”