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. outline • motivations • science goals • consensus of radio galaxies (RGs) hosted by massive galaxies in the local universe (z0.3) • formation mechanism of RGs • identification of interesting objects for detailed study • the sample • several statistics to look at • relationship with radio-quiet (RQ) population • dependence on the environment

3. motivation: to make the bright end of the luminosity function right Croton et al (2006)

4. 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

5. the sample • using NYU-VAGC DR6 LSS galaxy sample as parent sample, containing ~220,000 galaxies down to Mr–20.5 (about M*) • cross-matched with NVSS and FIRST surveys at 1.4 GHz to generate the largest radio galaxy catalog to date: 10,500 RGs stronger than 3mJy • improvements over previous studies • construction of several volume-limited subsamples • 90% of RGs have measured redshift • all RGs visually inspected to secure matches and measurement of fluxes • morphology information of radio sources • high S/N measurement of correlation functions • halo occupation distribution (HOD) modeling

6. whole sample M-20.5 volume-limited M-21.5 volume-limited bivariate luminosity function

7. 0.02z0.132 108,873 galaxies 2,253 RGs 2.1% of galaxies more luminous than M* have radio power logP23.12 fiber collision correction applied optical luminosity function

8. 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)

9. correlation function: HOD modeling • consider NRG=NRG,cen+NRG,sat • NRG,cen=1 if(MMmin) • NRG,sat=(M/M1) • HOD modeling suggests RGs are hosted by halos more massive than 1013 Msun (consistent with lensing results from Mandelbaum et al 2008)

10. 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 • 1435 galaxies, 85 RGs (~6%) • 62/134 (=46%) clusters host RGs • among these, 34 have RL BCGs • 44 clusters host only 1 RG, 20 of these are BCG • 25% of BCGs are RL • 3.9% of non-BCG galaxies are RL • NOTE: 2.1% of galaxies are RL globally BCGs clusters w/o RGs

11. RGs in massive halos: spatial distribution

12. 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

13. RGs in dense regions caution: small number of SF galaxies in the sample! no RLAGN–SF galaxy pairs at scales<1Mpc!

14. summary • 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: what’s the source? • work in progress • dissection of the bivariate LF • environment of high and low-excitation RL AGNs (e.g., FRI vs FRII) • relationship with X-ray and optical AGNs