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

Yu-Long Gao1,2, Jian-Hui Lian1,2, Xu Kong1,2, Ze-Sen Lin1,2, Ning Hu1,2, Hai-Yang Liu1,2,En-Ci Wang1   2017-05-29 00:20:06

1 CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, China; ylgao@mail.ustc.edu.cn; xkong@ustc.edu.cn

2 School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China

3 Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China

4 Nanjing Institute of Astronomical Optics & Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042, China

Received 2016 May 19; accepted 2017 January 3

Abstract 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 [O III]λ4363 above the 3σlevel, which allows a direct measurement of electron temperature and oxygen abundance. The emission linefluxes are corrected for internal dust extinction using the Balmer decrement method. With electron temperature derived from [O III]λλ4959, 5007/[O III]λ4363 and electron density from [S II]λ6731/[S II]λ6717, we obtain the oxygen abundances in our sample which range from 12 + log(O/H) = 7.63 (0.09 Z⊙) to 8.46 (0.6 Z⊙). We find an extremely metal-poor galaxy with 12 + log(O/H) = 7.63 ± 0.01. With multiband photometric data from FUV to NIR and Hαmeasurements, we also determine the stellar masses and star formation rates, based on the spectral energy distributionfitting and Hαluminosity, respectively. We find that our galaxies have low and intermediate stellar masses with 6.39≤log(M/M⊙) ≤9.27, and high star formation rates (SFRs) with−2.18 ≤ log(SFR/M⊙ yr−1) ≤ 1.95. We also find that the metallicities of our galaxies are consis-tent with the local Te-based mass–metallicity relation, while the scatter is about 0.28 dex. Additionally, assuming the coefficient ofα = 0.66, wefind 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.

  Key words: galaxies: abundances—galaxies: evolution—galaxies: starburst—star formation

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