(Proposal ID) S17A-083

(PI) Hayashi, Masao

(Proposal Title)
Probing metal-poor galaxy candidates with an extremely large [OIII] EW at z=0.8

(Abstract)
We propose a spectroscopic follow-up with FOCAS for less massive (< 5 x 10^{8} 
M_{sun}) galaxies with an extremely large [OIII](lambda5007) equivalent width 
(EW) in the rest-frame of gtrsim 500Angstrom at z ~ 0.84, which are selected 
as NB921 narrowband emitters by HSC-SSP ultra-deep survey. The extraordinary 
[OIII] EW implies that the galaxies are probable candidates of less massive, 
young (< 50 Myr) and metal poor (< 0.5 Z_{sun}) galaxies. Thus, we aim to 
spectroscopically confirm real less massive metal-poor galaxies at z ~ 0.84 by 
detecting several nebular emission lines. The various indices of emission line 
ratios allow us to probe the interstellar medium (ISM) condition of the gas-
phase metallicity (Z), ionization parameter, and electron density. Also, we 
correct the broadband photometry for the measured fluxes of major strong lines 
that can affect the photometry even in broadband, and then estimate stellar 
mass (M_star) and SFR by the SED fitting. We discuss the dependence of ISM 
state on M_{star} and SFR, and try to address at which evolutionary phase 
galaxies follow the scaling relations such as SFR--M_{star} and Z--M_{star} 
that massive galaxies follow tightly. Revealing the fundamental properties for 
such galaxies in early evolutionary phase is crucial for better understanding 
of galaxy formation and evolution.