Co-Evolution of Central Black Holes and Galaxies
c 2009 International Astronomical Union
Proceedings IAU Symposium No. 267, 2009
B.M. Peterson, R.S. Somerville, & T. Storchi-Bergmann, eds.
DOI: 00.0000/X000000000000000X

AGN and Galaxy Clustering at z = 0.3 – 3.0
using the Japanese Virtual Observatory
Yuji Shirasaki1 , Masahiro Tanaka2 , Masatoshi Ohishi1 , YoshihikoMizumoto1 , Tadafumi Takata1 , and Naoki Yasuda3
1National Astronoimcal Observatory of Japan,
2-21-1 Osawa, Mitaka, Tokyo, Japan
2
University of Tsukuba,
1-1-1 Tennodai, Tsukuba, Ibaraki, Japan3Institute for the Physics and Mathematics of the Universe Library, The University of Tokyo,
5-1-5 Kashiwa-no-ha, Kashiwa, Chiba, JapanAbstract. We present the result of the projected cross correlation analysis of the AGNs andgalaxies at redshifts from 0.3 to 3.0. It has been believed that the origin of AGN activity is
accretion of matters into a massive black hole at the center of a galaxy (e.g. Lynden-Bell(1969)).
To explain the activity of the AGNs, a large fraction of matters in the galaxy must be delivered
to the inner region on a short timescale (Hopkins et al.(2008)). One possible mechanism forcausing rapid gas inﬂows into the central region is a major galaxy merger between gas-richgalaxies (e.g. Kauﬀmann and Haehnelt (2000)). If this is the case, AGNs are expected to befound in an environment with higher galaxy density than that of typical galaxies. We investigatedenvironments of ∼ 750 AGNs, which was about ten times larger sample than those of previous
observations, and found signiﬁcant excess of galaxies around the AGNs at redshift range of 0.3
to 1.8. We used the Japanese Virtual Observatory (JVO) to obtain the Subaru Suprime-Camimages and UKIDSS data around known AGNs. The dataset accessed through the JVO are:Catalog of Quasars and Active Galactic Nuclei by Veron-Cetty et al.(2006), SDSS DR-5 Quasar
Catalog by Schneider et al.(2007), Subaru Suprime-Cam Reduced Image Archive of JVO, andUKIDSS DR2 catalog by Warren et al.(2007). We divided all the AGN samples into four redshiftgroups, z = 0.3–0.8, 0.8–1.5, 1.5–1.8, and 1.8–3.0. For each redshift group, the dataset was furtherdivided into a dimmer group (MV > −25) and a brighter group (MV < −25). We found thatthe correlation length of the high redshift bright sample (z = 1.5–1.8) was larger than thatof the low redshift dim sample (z = 0.3–0.8). We also found that the correlation length waslarger for the dim group at redshift range 0.8–1.5. These results can be explained by considering
the downsizing of mass assembly. More details can be found in Shirasaki et al. (2009). Our
result implies that the Japanese Virtual Observatory can be a powerful tool to investigate theco-evolution of central black holes and galaxies at the intermediate redshift universe.
Keywords. large-scale structure of universe, quasars: general, galaxies: evolution, galaxies:
formation, astronomical data bases: miscellaneous

References
Hopkins, P.F., Hernquist, L., Cox, T.J., and Keres, D., 2008, ApJS, 176, 356
Kauﬀmann, G., and Haehnelt, M. G., 2000, MNRAS, 311, 576
Lynden-Bell D., 1969, Nature, 223, 690
Schneider, D. P. et al., 2007 AJ, 134, 102
Shirasaki, Y. et al., 2009, arXiv:0907.5380, submitted to PASJ
Veron-Cetty, M.-P. and Veron, P. A&A, 455, 773
Warren, S. J. et al., 2007, arXiv:astro-ph/0703037

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