Two extremely metal-poor emission-line galaxies in the Sloan DigitalSky Survey

We present spectroscopic observations with the 3.6 m 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 + log O/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, SBS 0335–052W with 12 + log O/H = 7.12 ± 0.03 and I Zw 18 with 12 + log O/H = 7.17 ± 0.01.