  We present a panoramic narrow-band imaging survey of [OII] emitters in and
around the ClG J0218.3-0510 cluster at z=1.62 with Suprime-Cam on Subaru
telescope. 352 [OII] emitters were identified on the basis of narrow-band
excesses and photometric redshifts. We discovered a huge filamentary structure
with some clumps traced by [OII] emitters and found that the ClG J0218.3-0510
cluster is embedded in an even larger super-structure than the one reported
previously. 31 [OII] emitters were spectroscopically confirmed with the
detection of H-alpha and/or [OIII] emission lines by FMOS observations. In the
high density regions such as cluster core and clumps, star-forming [OII]
emitters show a high overdensity by a factor of more than 10 compared to the
field region. Although the star formation activity is very high even in the
cluster core, some massive quiescent galaxies also exits at the same time.
Furthermore, the properties of the individual [OII] emitters, such as star
formation rates, stellar masses and specific star formation rates, do not show
a significant dependence on the local density, either. Such lack of
environmental dependence is consistent with our earlier result by Hayashi et
al. (2011) on a z=1.5 cluster and its surrounding region. The fact that the
star-forming activity of galaxies in the cluster core is as high as that in the
field at z~1.6 may suggest that the star-forming galaxies are probably just in
a transition phase from a starburst mode to a quiescent mode, and are thus
showing comparable level of star formation rates to those in lower density
environments. We may be witnessing the start of the reversal of the local
SFR--density relation due to the "biased" galaxy formation and evolution in
high density regions at high this redshift, beyond which massive galaxies would
be forming vigorously in a more biased way in proto-cluster cores.
