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GMOS–IFU spectroscopy of the compact H ii galaxies Tol 0104−388 and Tol 2146−391: the dependence on the properties of the interstellar medium




Using GMOS–IFU spectroscopic observations of the compact H ii/blue compact dwarf galaxies Tol 0104−388 and Tol 2146−391, we study the spatial distribution of emission lines, equivalent width EW(Hβ), extinction c(Hβ), ionization ratios ([O iii] λ5007/Hβ, [S ii] λλ6717, 6731/Hα and [N ii] λ6584/Hα), kinematics and the chemical pattern (O/H, N/H and N/O) of the warm interstellar medium in these galaxies. We also investigate a possible dependence of these properties on the I(He ii λ4686)/I(Hβ) ratio and find no significant correlation between these variables. In fact, the oxygen abundances appear to be uniform in the regions where the He ii λ4686 emission line was measured. It can be interpreted in the sense that these correlations are related to global properties of the galaxies and not with small patches of the interstellar medium. Although a possible weak N/H gradient is observed in Tol 2146−391, the available data suggest that the metals from previous star formation events are well mixed and homogeneously distributed through the optical extent of these galaxies. The spatial constancy of the N/O ratio might be attributed to efficient transport and mixing of metals by starburst-driven supershells, powered by a plethora of unresolved star cluster in the inner part of the galaxies. This scenario agrees with the idea that most of the observed He ii λ4686 emission line is produced by radiative shocks, although other sources such as Wolf Rayet stars, high mass X-ray Binaries and O stars cannot be excluded.