1. Merging Galaxy Cluster Abell 2255 in Mid-Infrared
( Shim et al. 2011, ApJ, 727, 14 )
Hyunjin Shim
KNU
SSC
M. Im, H. M. Lee, M. G. Lee, S. J. Kim, H. S. Hwang, N. Hwang, J. Ko, J. C. Lee, S. Lim, H. Matsuhara, H. Seo, T. Wada, and T. Goto

2. Abell 2255, AKARI CLEVL CLEVL – G. H. Lee’s talk
Rich galaxy cluster at z=0.081 (c.f. NEP SC – J. Ko)
Membership determined based on the SDSS spectroscopy
X-ray observation suggests that A2255 is in post-merger stage
Rich ancillary data sets in X-ray (ROSAT, XMM-Newton, Chandra), UV (GALEX), optical (SDSS), radio (VLA)
Add X-ray plot (Feretti? – Chandra paper.. Contour)

3. Abell 2255, AKARI CLEVL 10arcmin x 10arcmin x 12
g-r
N3-N4
N3-S11
10arcmin x 10arcmin x 12
IRC [N3, N4, S7, S11, L15, L24]
Spitzer 24 & 70µm

4. Origins of MIR-Excess N3-S11 N3-S7 Star formation
Dust emission from the circumstellar dust shells around AGB stars
AGN
N3-S11
Age
is a dominant factor that determines MIR-excess
N3-S7

5. Origins of MIR-Excess
r<16.5 mag

6. Substructures and Kinematics
Local surface density of galaxies Σ5th
Substructures are identified, where local surface density is higher than average.

7. Substructures and Kinematics
A2255 is closely related to NEP Super Cluster (J. Ko’s talk)
At <2Mpc, redshift distribution is not single Gaussian.
z1=0.077±0.0027
z2=0.082±0.0017
Two components are gravitationally bounded: merging cluster

8. Environmental Dependence of Star Formation and Galaxy Transformation
log SSFR
Clustercentric distnce
log Σ5th
Star formation is NOT enhanced by the environment (e.g., distance from the center, local galaxy surface density)

9. Environmental Dependence
of Star Formation and Galaxy Transformation
(Number) fraction of intermediate MIR-excess galaxies
Clustercentric distnce
log Σ5th
No clear evidence that galaxies “in transition” prefer substructures

10. Conclusion
Relative fraction of intermediate MIR-excess galaxies increases at intermediate density region or 0.5<Rcl<2.0 Mpc
Cluster-scale merging suppresses the star formation through ram-pressure stripping

11. spectroscopic redshift catalogAD
Available now!
AKARI NEP-wide
spectroscopic redshift catalog
5.7 deg2
1852 objects (1207 from MMT/Hectospec; 645 from WIYN/Hydra)
R<22.5, R<20.5
Will be published soon,
Contact
Add IR SFR vs. halpha here?