%0 Generic %1 izotov2012hunting %A Izotov, Y. I. %A Thuan, T. X. %A Guseva, N. G. %D 2012 %K dwarfs gas low metallicity %T Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey: MMT and 3.5m APO observations %U http://arxiv.org/abs/1207.5971 %X We present 6.5-meter MMT and 3.5m APO spectrophotometry of 69 H II regions in 42 low-metallicity emission-line galaxies, selected from the Data Release 7 of the Sloan Digital Sky Survey to have mostly O III4959/Hbeta < 1 and N II6583/Hbeta < 0.1. The electron temperature-sensitive emission line O III 4363 is detected in 53 H II regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 H II regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12 + log O/H ~ 7.1 to ~ 7.9, with 14 H II regions in 7 galaxies with 12 +log O/H < 7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12 +log O/H < 7.35) emission-line galaxies known in the local universe. There appears to be a metallicity floor at 12 +log O/H ~ 6.9, suggesting that the matter from which dwarf emission-line galaxies formed was pre-enriched to that level by e.g. Population III stars.

@misc{izotov2012hunting, abstract = {We present 6.5-meter MMT and 3.5m APO spectrophotometry of 69 H II regions in 42 low-metallicity emission-line galaxies, selected from the Data Release 7 of the Sloan Digital Sky Survey to have mostly [O III]4959/Hbeta < 1 and [N II]6583/Hbeta < 0.1. The electron temperature-sensitive emission line [O III] 4363 is detected in 53 H II regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 H II regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12 + log O/H ~ 7.1 to ~ 7.9, with 14 H II regions in 7 galaxies with 12 +log O/H < 7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12 +log O/H < 7.35) emission-line galaxies known in the local universe. There appears to be a metallicity floor at 12 +log O/H ~ 6.9, suggesting that the matter from which dwarf emission-line galaxies formed was pre-enriched to that level by e.g. Population III stars.}, added-at = {2012-07-26T15:00:46.000+0200}, author = {Izotov, Y. I. and Thuan, T. X. and Guseva, N. G.}, biburl = {https://www.bibsonomy.org/bibtex/2d32d39f6c22e1a0f2cf4b8ebc97467f1/miki}, description = {[1207.5971] Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey: MMT and 3.5m APO observations}, interhash = {98e0dc43b5d3377639c316fb15565f13}, intrahash = {d32d39f6c22e1a0f2cf4b8ebc97467f1}, keywords = {dwarfs gas low metallicity}, note = {cite arxiv:1207.5971Comment: 35 pages, 6 figures, accepted for publication in Astronomy and Astrophysiscs}, timestamp = {2012-07-26T15:00:46.000+0200}, title = {Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey: MMT and 3.5m APO observations}, url = {http://arxiv.org/abs/1207.5971}, year = 2012 }