Hunting for extremely metal-poor emission-line galaxies in the Sloan
Digital Sky Survey: MMT and 3.5m APO observations
Y. Izotov, T. Thuan, and N. Guseva. (2012)cite arxiv:1207.5971Comment: 35 pages, 6 figures, accepted for publication in Astronomy and Astrophysiscs.
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 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.
Description
[1207.5971] Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey: MMT and 3.5m APO observations
%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
}