出版社:SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要:We discuss the environmental dependence of the galaxy evolution based on deep panoramic imaging
of two distant clusters, CL0016+1609 at z = 0.55 and RXJ0152.7−1257 at z = 0.83, taken
with Suprime-Cam on Subaru as part of the PISCES project. By combining with the SDSS data
as a local counterpart for comparison, we construct a large sample of galaxies that spans wide
ranges in environment, time, and stellar mass (or luminosity). Based on local and global densities
of galaxies, we classify three environments: field, group, and cluster. Then we focus on the
color-magnitude relation of galaxies. In particular, we quantify how the color-magnitude relation
is built-up as a function of time, environment, and mass. In the field environment, there is no
clear color-magnitude relation at z = 0.83, while a clear relation is seen at lower redshifts, especially
at the bright end. In groups, a relation is visible only at the bright end (MV < −20) at
z=0.83. The relation is found to extend down to our magnitude limit in groups at lower redshifts.
Clusters have a clear relation down to the magnitude limit at all redshifts considered here. We
confirm the ‘down-sizing’ in the star formation recently reported both at low and high redshifts,
where massive galaxies complete their star formation earliest and the truncation of star formation
is propagated to smaller objects as time progresses. Our results suggest that ‘down-sizing’ is yet
at its earlier stage in lower density regions, while it is more proceeded in high density regions. All
in all, it is likely that the formation and evolution of galaxies are the earliest in massive systems
and in high density regions, and it proceeds to less massive systems and to lower density regions.