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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). credit: NRAO, J. Uson. outline. motivation construction of the sample

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statistical properties of radio galaxies in the local universe

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

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

motivation sz surveys are happening

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

the sample
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
correlation function
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)
correlation function hod modeling
correlation function: HOD modeling
  • halo occupation distribution modeling suggests RGs are hosted by halos more massive than 1013 Msun
rgs in massive halos halo occupation number
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

rgs in dense regions
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

rgs in dense regions1
RGs in dense regions

no RLAGN–SF

galaxy pairs at

scales<1Mpc!

conclusion
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
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