Deep VLT spectroscopy of the blue compact dwarf galaxies Tol 1214 – 277 and Tol 65 ⋆

We present VLT spectroscopic observations with different spectral resolutions and different slit orientations of the two metal-deficient blue compact dwarf (BCD) galaxies Tol 1214–277 and Tol 65. The oxygen abundances in the brightest H ii regions of Tol 1214–277 and Tol 65 are found to be 12 + log O/H = 7.55 ± 0.01 and 7.54 ± 0.01, or Z⊙/24 . The nitrogen-to-oxygen abundance ratios in the two galaxies are log N/O = –1.64 ± 0.03 and –1.60 ± 0.02 and lie in the narrow range found for other most metal-deficient BCDs. The helium mass fraction derived in several H ii regions in both galaxies is consistent with a high primordial helium mass fraction, Yp ∼ 0.244. We confirm the detection of the high-ionization forbidden emission line [Fe v] λ4227 in the spectrum of Tol 1214–277. Additionally, weak [Ne iv] λ4725, [Fe vi] λ5146, λ5177, and [Fe vii] λ5721, λ6087 emission lines are detected in the high-resolution spectrum of Tol 1214–277. The detection of these lines implies the presence of hard radiation with photon energy in the range ∼ 4 – 8 Ryd. Emission lines are detected in the spectra of eight galaxies in the fields of Tol 1214–277 and Tol 65. Seven of these galaxies are background objects, while one galaxy has a redshift close to that of Tol 1214–277. Situated at a projected distance of ∼ 14.5 kpc from Tol 1214–277, this galaxy is probably a companion of the BCD.