(Proposal ID) S16A-024

(PI) Tanaka, Masayuki

(Proposal Title)
Resolved Kinematics of Massive Compact Star Forming Galaxies at z~2.5

(Abstract)
Recent observations show that as much as ~50% of the most massive galaxies are 
already passively evolving at z~2 and this early quenching has challenged our 
framework of galaxy formation. Physical processes driving such early quenching 
still unfortunately remain unidentified despite the enormous effort. Very 
recently, a possible progenitor population of z~2 quiescent galaxies has been 
identified; massive compact {star forming} galaxies at z=2-3. These galaxies 
share similar properties to the quiescent galaxies, except that they are 
actively forming stars. Natural-seeing spectroscopic follow-up observations 
revealed unusually broad emission lines (~300 km s^{-1}), similar in width to 
absorption lines in quiescent galaxies. They are currently the most promising 
progenitor candidates, but the evolutionary link is not established yet --- 
they could still be compact disk galaxies (i.e., non-progenitors) because disk 
rotation could account for the line width. Here we propose a pilot OSIRIS-LGSAO
 observation to obtain spatially resolved Halpha kinematics of two compact 
star forming galaxies.  Once we establish the observing strategy in this pilot 
observation, we will move on to construct a larger statistical sample to probe 
the link and resolve the long-standing issue of the quenching physics.