S21A0121

We propose to make a wide-area (630 arcmin²) imaging survey by using three medium K-band filters on Subaru/SWIMS. We will measure the number density of massive quiescent galaxies at z=4.2−4.8 in general fields for understanding when and how they are formed in the early universe. 5.3±2.3 massive quiescent galaxies are expected to be identified in the survey volume, if assuming that the number density decreases by a factor of two from z=3−4 to z=4−5. The existence of a substantial population of massive quiescent galaxies at z>4 would suggest that they are unexpectedly often formed at even higher redshift (z>6). On the other hand, even the case of non-detection would suggest a strong redshift evolution of the number density of massive quiescent galaxies. Therefore, the proposed observations will offer a new insight into the formation histories of massive galaxies in the epoch of reionization. The survey depth and the filter choice are optimized for making spectroscopic follow-up observations with existing facilities. We also note that the addition of the medium K-band photometry further enhances the legacy value of the deep fields, COSMOS-DASH and CANDELS (GOODS-N and EGS), where an extensive broad-band data set is available.

This document was translated from L^AT_EX by H^EV^EA.