jvo
Far and Bright AGN

0. Abstract
Japanese Virtual Observatory (JVO) is an
integrated database system developed byAstronomy Data Center of NAOJ. By accessing
the JVO, one can retrieve reduced Subaru
Suprime-Cam images, and also can accessseamlessly to any Virtual Observatorycompliant data services of the world. This
poster describes an early result from the JVO;
study of the clustering of galaxies around anAGN. Using the data obtained through the JVO,
we measured correlation length between AGN andgalaxy in ten times higher statistics thanever achieved at intermediate redshifts(z=1~2). We find an indication of enhanced
clustering at distance less than 1Mpc from abright AGN sample (Mb < -25)

1. Introduction

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Near and Dimmer AGN
Flattening ?

Figure 2: Absolute magnitude-redshift distribution of theanalyzed AGNs.

Depletion ?

Figure 4: The distribution of Galaxy number density foreach absolute magnitude range of AGN.

Figure 3: Limiting magnitude of observations for all the AGN
samples. The peak around mag~20 corresponds to UKIDSS data,
the peak around m~24 corresponds to the SuprimeCam data.

According to the hierarchical galaxy formation
model, it is assumed that a large galaxy has been
formed through the collisions and mergers of smaller
galaxies. During the galaxy evolution, a massive BH is
1. Create a catalog from Suprime-Cam image using theformed at the center of the galaxy, and accretion ofSextractor. Create a multi-band catalog whichmatters into the BH radiates large amount of energy,
consists of data in nine bands (B, V, R, I, i’, z’,which is observed as an AGN. It is, therefore,J, H, K) at maximum.
expected that the AGN is located at higher density
2. Create a number density histogram of galaxy as aregion where probability of the galaxy collision isfunction of distance from the AGN. Unobserved areahigh.
due to bad pixel, bright object, no data iscorrected.
Using the SDSS data, the clustering property of AGN
3. Remove samples which is strongly affected by theand galaxy has been measured upto z~0.6. To extend
unassociated cluster of galaxies and/or
this measurement to higher redshifts AGN, deep imaging
inhomogeneity of the observations by applying 3
observations are necessary. Using the data archive of
sigma deviation cut and c2 cut to the histogram.
Subaru Suprime-Cam, it is possible to measure the4. For each subset of AGN samples grouped by its
distribution of galaxies around an AGN at theredshift and brightness, the averaged number density
intermediate redshift (z=1~2), which is difficult tohistogram is calculated. Assuming the number density
be carried out with a smaller telescope. At thisprofile of the form of Eq (1), we derive correction
redshift range the formation rate of the AGN reaches alength r0 for a fixed value of γ = 0.8.
maximum, so it is interesting to see the relation AGN(1)
activity and its environment, which may reveal afundamental clue for the mechanism of AGN evolution.

Flattening ?

3. Analysis method

2. Dataset

Depletion ?

Figure 5: The distribution of galaxy number density foreach redshift range of AGN.

Figure 6: Dependence of the correlation length r0 on theabsolute magnitude of AGNs.

(2)

We used the following dataset: AGN Catalog by Veron et al (2006)(3)

 QSO Catalog (SDSS DR-5)
 Subaru Suprime-Cam reduced image
 UKIDSS DR2
We searched the Suprime-Cam images and UKIDSS IR
data around the AGNs listed in the Veron et al andSDSS AGN catalog, .
We analyzed for 744 AGN samples.
The celestial distribution of the AGNs are shown inFigure 1.

ρ0 : average number density of galaxy at AGN’s redshiftρ(r) : observed number density as a function of distance from the AGN.
rp : perpendicular distance from the AGN
Γ: The Gamma function
Ni(rp) : projected number count of galaxies at distance rp from i-th AGN.
Si(rp) : effective area corresponding to the number of Ni(rp)ρi,0 : ρ0 for the i-th AGN
nbg : Back and foreground galaxy number density

The average number density is derived from Luminocity
Function obtained by Gabasch et al.(2004,2007)、Cirasuolo etal (2007).

4. Result• We detected a clustering signal for datasetwith redsfhit < 1.8 (Figure 5).
• We obtained a consistent result with theexisting measurements for low redshift sample(z<1.2) (Figure 4,5). No significant redshiftdependence was measured. (Figure 7).

Figure 1 : The celestial distribution of the AGN analyzed
in this work.(in equatorial coordinate)• Bright (and inevitably higher redshift) AGNs
have a tendency showing higher clustering
property within 1 Mpc.

Figure 7: Dependence of the correction length r0 on theredshift of AGNs

5. Summary•We successfully measured the properties of AGN andgalaxy clustering for wider redsfhit and absolutemagnitude spaces in higher statistics than the otherobservations have made. The near and dimmer AGN havean environment similar to that of a typical galaxy,so the scenario that the galaxy merger trigger theAGN activity is unlikely for these AGNs. In the caseof far and brighter AGN, overdensity is slightly
measured at less 1Mpc from the AGN and thedistribution is nearly flat at this distance range,
which indicates these AGN is not necessarily locatedat the center of the galxy distribution.

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