1. Yuka Katsuno Uchimoto Institute of Astronomy, University of Tokyo
Subaru User’s Meeting Subaru/MOIRCS Near-Infrared Imaging in the z=3.1 Proto-Cluster Region
Yuka Katsuno Uchimoto
Institute of Astronomy, University of Tokyo
M. Kajisawa (NAOJ), T. Yamada, T. Ichikawa (Tohoku Univ.), R. Suzuki, C. Tokoku (NAOJ), M. Konishi, T. Yoshikawa (NAOJ/Tohoku Univ.), I. Tanaka, M. Akiyama, K. Omata, T. Nishimura (NAOJ), Y. Matsuda (Kyoto Univ.), R. Yamauchi, and T. Hayashino (Tohoku Univ.)

2. Introduction
The biased galaxy formation models in the universe dominated by cold dark matter suggest that galaxy formation preferentially occurs in the region with relatively high density at the larger scale.
By observing high density region of galaxies at high-z, we will find the progenitors of present-day nearby clusters of galaxies, namely proto-clusters, which will enable us to investigate how galaxies have formed and evolved in the high density environment.
NIR observation will reveal how much of stellar mass has already formed and assembled in such high density region of star-forming galaxies at z>2.
z＝3
z＝0
114 h-1 Mpc
Benson et al. 2001

3. The NIR survey of the proto-cluster at z=3.1 around the SSA22 field
The proto-cluster is extended over ~ 60 Mpc and the structure has a three-dimensional filamentary appearance.
The volume densities of z=3.1 LBGs and LAEs are 6 times higher than blanking fields.
Our JHK survey covers 100 arcmin2 area.
The field which includes the two most luminous Lya blobs, LAB1 and LAB2, is used for this study.
Our survey
LAE
Matsuda et al. 2004
LAB1
LAB2
LAB
LAA
LAB2
LAB1
This study
Hayashino et al. (2004)
The SSA22-sb1 field obserbed by Hayashino et al. (2004). The contour shows the high density region of LAEs.

4. Lya Blobs (LABs) Extended, bright, and radio-quiet Lya-emitting clouds
Physical extent ~ kpc
Lya luminosity >1043 erg s-1
They are typically seen in the proto-cluster region at high-z.
There are 35 LABs along the LAE structure in the SSA22-sb1 field (Matsuda et al. 2004).
Matsuda et al.
(2004)

5. Data NIR : MOIRCS JHK data taken in 2005 & 2006. 21.7 arcmin2
Optical : Sup-Cam data in Hayashino et al. (2004).
UV : Un-data in Steidel et al. (2003) .
UnBVRizJHKs-bands are used for the photometric redshift and the SED fitting for the stellar mass estimation.

6. Result1: The selection & surface density of DRGs
The surface density of DRGs is 1.29 arcmin-2 at K<23.35 (or K Vega < 21.5), which is comparable with that in GOODS-N by, 1.36 ±0.26 arcmin-2 to the same depth.
(a) The color-magnitude diagram of the K-selected objects. The horizontal dashed line shows J-K=1.4. The expected color-magnitude relations of cluster galaxies calculated by Kodama & Arimoto (1997) for Coma cluster model with the formation redshift at zf=4.1 and zf=5.3 are plotted with the squares and the crosses, respectively. The points indicate the location of model galaxies with the rest-frame V-band luminosity from MV=－17 to MV=－22 at z=0.
(b) Differential number counts for DRGs in our observed field (filled circles, red).

7. Photometric Redshift of the K-selected Sources
UnBVRizJHKs-bands are used for the photometric redshift.
HyperZ code (Bolzonella et al. 2000) with the template spectrum derived from GALAXEV (Bruzual & Charlot 2003).
At z~3, the uncertainty of the photo-z is Dz~0.5.
We pick up the objects with 2.6 < zphot < 3.6 as the candidates at z=3.1.
z=3 LBGs
zphot
zspec

8. Result2: DRGs & the photo-z selected galaxies
LAB2
LAB1
The distribution of the NIR-selected objects is correlated with the sample of LABs as well as LBGs.
(a) DRGs with K<23.5
(c) LABs, LAEs and LBGs
LAB2
LAB2
LAB1
LAB1
(b) zphot= objects
with K<23.5

9. LAEs are not associated with K-band sources.
The density of the NIR-selected objects shows the notable excess within 1.0 arcmin (1.9 Mpc at z=3.1 in comoving scale) around the two distinctive giant LABs, namely LAB1 and LAB2.
LAEs are not associated with K-band sources.
(a) The mean surface number density of DRGs with K<23.5 around optically selected galaxies. The horizontal axis is a radius from LABs, LAEs or LBGs. The surface densities of DRGs from LAB1 and LAB2, LABs, LAEs, LBGs, and LABs excluding LAB1 and LAB2 are shown as crosses (cyan), open circles (blue), open squares (green), open triangles (magenta), and inverted triangles (orange), respectively.
(b) The mean surface number density of zphot= objects with K<23.5 around optically selected galaxies.

10. Result3. The NIR properties of LABs
The stellar mass is derived from the SED fitting with GALAXEV (Bruzual & Charlot 2003) using UnBVRizJHKs data. The stellar mass of the LAB counterparts ranges from 4x109 to 1x1011 Msun.
Ks-band images around eight LABs at z=3.1. The size of each panel is 25'', which corresponds to ~ 190 kpc at z=3.1.
The green and red contours are the isophotal levels of NB497 and R-band images, respectively. 30
LABs, LAEs, LBGs 2 8 1 20 7 31 16

11. LBG at z=3.1 J H K
The green and red contours are the isophotal levels of NB497 and R-band images, respectively.

12. Result4. The stellar mass of K-selected objects associated with LABs
The relation between Lya luminosity and the integrated stellar mass of the K-selected objects which are associated with each LAB. Surface brightness of Lya vs. the stellar mass is also shown.
The figures suggest that the more massive galaxies are seen in the brighter LABs and the LABs with the higher surface brightness in Lya.
This result implies the origin of the Lya emission of LABs may be related with their stellar mass or their previous star-formation history.

13. How unique are LAB1 and LAB2 among the 35 LABs in the proto-cluster?
LAB1 & LAB2 are the largest and the most luminous in Lya.
They are located at the intersection of filamentary structure of LAEs.
Matsuda et al. (2006)
Matsuda et al. (2006)

14. Summary
We presented the results of deep near-infrared imaging observations of the z=3.1 proto-cluster region in the SSA22a field taken by MOIRCS mounted on the Subaru Telescope. We observed 21.7 arcmin2 field to the depths of J=24.5, H=24.3, and K=23.9 (f1”.1, 5s).
We examined the distribution of the K-selected galaxies at z~3 by using the simple color cut for distant red galaxies (DRGs) as well as the　photometric-redshift selection technique. The marginal density excess of DRGs and the photo-z selected objects are found around the two most luminous Lya blobs (LABs).
We investigated the correlation between the K-selected objects and the LABs, and found that several galaxies with stellar mass Ms = 109~1011 MSun exist in vicinity of LABs, especially around the two most luminous ones.
We also found 7 of the 8 LABs in the field have plausible Ks-band counterparts and　the sum of the stellar mass possibly associated with LABs correlates with the luminosity and surface　brightness of them, which implies that the origin of Lya　emission may be closely correlated with their stellar mass or their previous star formation phenomena.