Statistical properties of radio galaxies in the local universe
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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

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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


Motivation making the bright end of the luminosity function right

motivation: making the bright end of the luminosity function right


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 massive halos spatial distribution

RGs in massive halos: spatial distribution


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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