(Proposal ID) S16A-145

(PI) Kojima, Takashi

(Proposal Title)
Evolution of N/O Abundance Ratio Probed with T_e Determined Galaxies

(Abstract)
We propose FMOS J-long spectroscopy for the sample of 16 galaxies with 
electron temperature (T_e) determinations from [Oiii]4363 lines, supplemented 
with ~ 120 galaxies with strong nebular line measurements, at z~1 in the DEEP2 
survey fields. We will obtain FMOS spectra with [Nii]6583 and Halpha lines. 
Having these FMOS spectra for the well characterized galaxy sample, we aim to 
estimate N/O abundance ratios and to test whether the N/O abundance ratio 
evolves towards high-z that is one of the key questions of inter-stellar 
medium evolution today (e.g. Steidel et al. 2014, Shapley et al. 2015). 
There are two major uncertainties of N/O abundance ratio measurements, 
metallicities and ionization parameters, in a reasonable electron density 
value range. Because we have robust metallicities and ionization parameters 
for our T_e-determined galaxies. We will obtain N/O abundance ratios of these 
galaxies free from the metallicity and ionization parameter uncertainties. 
The expected uncertainties of our N/O abundance ratio estimates are 0.2 dex on 
the individual source basis and 0.1 dex on average that is good enough to test 
the evolution of N/O abundance ratio towards z~1. This program exploits FMOS's 
wide-field capability, which should be completed before the FMOS decommission 
in S16A.