Statistical Properties of Radio Galaxies in the local Universe

1. 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)

2. credit: NRAO, J. Uson outline • motivation • construction of the sample • relationship with radio-quiet (RQ) population • dependence on the environment • formation mechanism of radio galaxies (RGs) NGC1316 + Fornax A

3. credit: CXO Carlstrom et al (2002) motivation: SZ surveys are happening! Atacama Cosmology Telescope in construction see Lin et al (0805.1750) for estimation of effects of radio sources on SZ signal

4. motivation: making the bright end of the luminosity function right

5. the sample • using NYU-VAGC DR6 LSS galaxy sample as parent sample, containing ~220,000 galaxies with measured redshifts down to Mr–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

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

7. correlation function: HOD modeling • halo occupation distribution modeling suggests RGs are hosted by halos more massive than 1013 Msun

8. RGs in massive halos: halo occupation number • count galaxies and RGs at Mr–20.5 in 134 X-ray clusters from ROSAT all-sky survey • number of galaxies goes as M0.8 • 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

9. RGs in massive halos: spatial distribution

10. 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Mr–20.5 • within ~0.5 Mpc, RL galaxies always have higher number of neighbors than RQ ones Mpc

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

12. 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