Abstract
We present spectroscopic observations with the 3.6m ESO telescope of two emission-line galaxies, J2104-0035 and J0113+0052, selected from the Data Release 4 (DR4) of the Sloan Digital Sky Survey (SDSS). From our data we determine the oxygen abundance of these systems to be respectively 12+logO/H = 7.26+/-0.03 and 7.17+/-0.09, making them the two most metal-deficient galaxies found thus far in the SDSS and placing them among the five most metal-deficient emission-line galaxies ever discovered. Their oxygen abundances are close to those of the two most metal-deficient emission-line galaxies known, SBS0335-052W with 12+logO/H = 7.12+/-0.03 and I Zw 18 with 12+logO/H = 7.17+/-0.01.
Highlights
Metal-deficient emission-line galaxies at low redshifts are the most promising young galaxy candidates in the local Universe (Guseva et al 2003; Izotov & Thuan 2004b)
We present here new spectroscopic observations of two galaxies, J2104–0035 and J0113+0052 (Fig. 1), from the list of extremely low-metallicity candidates selected from the Sloan Digital Sky Survey (SDSS)
The [O ii] λ3727 line is beyond the wavelength range of the SDSS spectrum of J0113+0052 while
Summary
Metal-deficient emission-line galaxies at low redshifts are the most promising young galaxy candidates in the local Universe (Guseva et al 2003; Izotov & Thuan 2004b). Since the [O ii] λ3727 line is out of the observed wavelength range in the SDSS spectra for all galaxies with a redshift z lower than 0.02, we use the [O iii] λ4959, λ5007 and [N ii] λ6583 emission to pick out extremely low-metallicity galaxy candidates. Following this strategy we selected ∼20 galaxies with [O iii]λ4959/Hβ
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