(Proposal ID) S17A-085

(PI) Koyama, Yusei

(Proposal Title)
Pinpointing dusty star-forming regions within starburst galaxies in z=0.4 cluster

(Abstract)
Our recent NB H alpha survey of a rich cluster at z=0.4 (CL 0939+4713) with 
Suprime-Cam has unveiled a large number of  "red H alpha emitters (red-HAEs)" 
in the cluster surrounding groups, where the colours/morphologies of galaxies 
sharply change. This coincidence of colour/morphology transition and the red-
HAEs population suggests that red-HAEs are strong candidates for the 
progenitors of local cluster S0s. We here propose more detailed IFU 
spectroscopy of this key population to perform a complete mapping of H beta, 
[OIII], H alpha, and [NII] lines within individual galaxies. Our goals are:
(1) By mapping dust extinction levels within the galaxies using H alpha/H beta
ratio, we will make pixel-by-pixel SFR--M_{star} diagram to see "where in 
galaxies" the SF activity is boosted or truncated; (2) By making pixel-by-pixel
BPT diagram, we will identify the presence (or absence) of AGNs in the central
few kpc of the galaxies; (3) By performing the same IFU observations for the 
"blue-HAEs", we will identify how special the red-HAEs are. Pixel-by-pixel 
approach proposed here will allow us (for the first time) to pinpoint the 
location of rapid stellar build-up inside the progenitors of present-day 
cluster S0 galaxies, and shed new lights on the nature of red SF galaxies.