We have recently detected, from X-shooter spectroscopic data of a bright quasar, a Lyman limit system (LLS) at zabs = 1.54 with carbon overabundance over iron [C/Fe] = +2.2 at [Fe/H] = −1.6 (Zou et al, 2020). The neutral column density of log N(H i) = 18.18 means that the gas cannot be shielded from the outside UV flux. Therefore it is very surprising to detect C i except if the carbon metallicity is high. It is plausible to be the first carbon-enhanced metal-poor (CEMP)-Lyman Limit System (LLS). Detection of such pristine gas at high redshift would have opened a new window on the study of first stars formation history. Accurate column densities are obtained only with high resolution data. Therefore, we propose to use Subaru HDS to obtain a high SNR and high resolution spectrum of the bright quasar to derive accurate abundance measurements.
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