In order to understand how massive galaxies formed in a high-density enviroments at z > 2, we analyzed Suprime-Cam (B, V, i’ band) and MOIRCS (J, H, Ks band) data of the protocluster near 53W002 discovered as a high density structure od Lyman Alpha Emitters (LAEs) at z=2.4. We applied NIR color selection technique with JHKs band to select massive galaxy candidates in the protocluster. We then investigated optical and NIR colors of the selected member candidates and compared them with color tracks of population synthesis models from the GALAXEV library.
We found that those galaxies with the reddest NIR colors of J-Ks (AB) > 2 show relatively blue optical colors, which suggest that those are dusty star-forming galaxies with relatively low SSFRs. On the other hand, those with J-Ks (AB) ~ 1.5 have optical and NIR colors which are consistent with quenched/passive evolving models.
In addition, we compared spatial distribution of those quenched galaxies seems to be offset from the high-density structures of LAEs, while the dusty star-forming galaxies are located along the structure. These results may indicate that the evolutionary phases of massive galaxies vary with location within the protocluster.