A sample of metal-poor galaxies identified from the LAMOST spectral survey

We present a sample of 48 metal-poor galaxies at $z<0.14$ selected from 92 510 galaxies in the LAMOST survey. These galaxies are identified by their detection of the auroral emission line $\left[OIII\right]\lambda$4363 above the $3\sigma$ level, which allows a direct measurement of electron temperature and oxygen abundance. The emission line fluxes are corrected for internal dust extinction using the Balmer decrement method. With electron temperature derived from $\left[OIII\right]\lambda \lambda 4959,5007/\left[OIII\right]\lambda 4363$ and electron density from $\left[SII\right]\lambda 6731/\left[SII\right]\lambda 6717$, we obtain the oxygen abundances in our sample which range from $12+log\left(O/H\right)=7.63(0.09Z_{\odot }$) to 8.46 ($0.6Z_{\odot }$). We find an extremely metal-poor galaxy with $12+log\left(O/H\right)=7.63\pm 0.01$. With multiband photometric data from FUV to NIR and $H\alpha$ measurements, we also determine the stellar masses and star formation rates, based on the spectral energy distribution fitting and $H\alpha$ luminosity, respectively. We find that our galaxies have low and intermediate stellar masses with $6.39\le log\left(M/M_{\odot }\right)\le 9.27$, and high star formation rates (SFRs) with $-2.18\le log\left(SFR/M_{\odot }{yr}^{-1}\right)\le 1.95$. We also find that the metallicities of our galaxies are consistent with the local $T_e$-based mass–metallicity relation, while the scatter is about 0.28 dex. Additionally, assuming the coefficient of $\alpha =0.66$, we find most of our galaxies follow the local mass–metallicity–SFR relation, but a scatter of about 0.24 dex exists, suggesting the mass–metallicity relation is weakly dependent on SFR for those metal-poor galaxies. (paper)