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

P. Lagos, E. Telles, A. Nigoche-Netro, E. R. Carrasco

Abstract
Using GMOS–IFU spectroscopic observations of the compact H_II/BCD galaxies Tol 0104-388 and Tol 2146-391, we study the spatial distribution of emission lines, equivalent width EW(Hß), extinction c(Hß), ionization ratios ([OIII] λ5007/Hß, [SII] λλ6717,6731/Hα and [NII] 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(Hß) 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 super-shells, 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, in our sample of galaxies, is produced by radiative shocks, although other sources such as Wolf Rayet stars, high mass X-ray Binaries and O stars cannot be excluded.

Keywords
galaxies: abundances – galaxies: dwarf – galaxies: individual: Tol 0104-388 – galaxies: individual: Tol 2146-391 – galaxies: ISM

Monthly Notices of the Royal Astronomical Society
Volume 427, Page 740
November 2012

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