Statistical Properties of Radio Galaxies in the local Universe Yen-Ting Lin Princeton University Pontificia Universidad Católica de Chile Yue Shen, Michael Strauss, Ragnhild Lunnan (Princeton), Zheng Zheng (IAS)

outline motivation construction of the sample relationship with radio-quiet (RQ) population dependence on the environment formation mechanism of radio galaxies (RGs) credit: NRAO, J. Uson NGC Fornax A

motivation: SZ surveys are happening! credit: CXO Carlstrom et al (2002) Atacama Cosmology Telescope in construction see Lin et al ( ) for estimation of effects of radio sources on SZ signal

motivation: making the bright end of the luminosity function right

using NYU-VAGC DR6 LSS galaxy sample as parent sample, containing ~220,000 galaxies with measured redshifts down to M r  –20.5 cross-matched with NVSS and FIRST surveys at 1.4 GHz to generate the largest radio galaxy catalog to date: 10,500 RGs studying luminosity function and clustering properties from volume- limited subsamples the sample

correlation function both galaxies and RGs are volume-limited and subject to same optical luminosity cut (M r  –21.5) RGs (red) more strongly clustered than galaxies (blue) clustering length comparable to groups of galaxies (~10h -1 Mpc)

correlation function: HOD modeling halo occupation distribution modeling suggests RGs are hosted by halos more massive than M sun

RGs in massive halos: halo occupation number count galaxies and RGs at M r  – 20.5 in 134 X-ray clusters from ROSAT all-sky survey number of galaxies goes as M 0.8 occupation number of RGs not a strong function of cluster mass 1440 galaxies, 85 RGs (~6%) 61/134 (=45%) clusters host RGs among these, 34 have RL BCGs 42 clusters host only 1 RG, 19 of these are BCG 25% of BCGs are RL 4% of non-BCG galaxies are RL NOTE: only 1.9% of galaxies are RL globally BCGs clusters w/o RGs

RGs in massive halos: spatial distribution

RGs in dense regions excess number of neighbors –1000 RGs, 1000 RQ galaxies matched to optical luminosity, apparent magnitude, and redshift –count nearby objects out to 2 Mpc from SDSS photometric catalog, within –23.5  M r  –20.5 –within ~0.5 Mpc, RL galaxies always have higher number of neighbors than RQ ones Mpc

RGs in dense regions no RLAGN–SF galaxy pairs at scales<1Mpc!

conclusion observations: –given optical luminosity and color, RGs are more strongly clustered than the corresponding RQ galaxy sample –large scale clustering implies hosts are group or cluster-sized halos –RGs very centrally concentrated towards halo center ingredients for RL AGN phenomenon –dense environment –presence of intracluster/intragroup gas: confining pressure? –low level supply of gas: mass loss from old stars? further tests –halo occupation number in optical-selected clusters –environment of high and low-excitation RL AGNs (e.g., FRI vs FRII) –matching with X-ray AGNs