Oxygen abundance variations in the system of the two blue compact dwarf   galaxies SBS 0335-052E and SBS 0335-052W
  We present 3.6m ESO telescope spectroscopic observations of the system of the two blue compact dwarf galaxies SBS 0335-052W and SBS 0335-052E. The oxygen abundance in SBS 0335-052W is 12 + log O/H = 7.13 +/- 0.08, confirming that this galaxy is the most metal-deficient emission-line galaxy known. We find that the oxygen abundance in SBS 0335-052E varies from region to region in the range from 7.20 to 7.31, suggesting the presence of an abundance gradient over a spatial scale of 1 kpc. Signatures of early carbon-type Wolf-Rayet stars are detected in cluster 3 of SBS 0335-052E, corresponding to the emission of three to eighteen WC4 stars, depending on the adopted luminosity of a single WC4 star in the CIV 4658 emission line. 
P. Papaderos (1), Y.I. Izotov (2), N.G. Guseva (2), T.X. Thuan (3),   K.J. Fricke (1) ((1) Institute for Astrophysics, Unive...