Massive star formation in Wolf-Rayet galaxies: II. Optical spectroscopy
  results
  (Abridged) We have performed a comprehensive multiwavelength analysis of a
sample of 20 starburst galaxies that show the presence of a substantial
population of very young massive stars. In this paper, the second of the
series, we present the results of the analysis of long-slit
intermediate-resolution spectroscopy of star-formation bursts for 16 galaxies
of our sample. We study the spatial localization of the WR stars in each
galaxy. We analyze the excitation mechanism and derive the reddening
coefficient, physical conditions and chemical abundances of the ionized gas. We
study the kinematics of the ionized gas to check the rotation/turbulence
pattern of each system. When possible, tentative estimates of the Keplerian
mass of the galaxies have been calculated. Our analysis has revealed that a
substantial fraction of the galaxies show evidences of perturbed kinematics.
With respect to the results found in individual galaxies, we remark the
detection of objects with different metallicity and decoupled kinematics in
Haro 15 and Mkn 1199, the finding of evidences of tidal streams in IRAS
08208+2816, Tol 9 and perhaps in SBS 1319+579, and the development of a merging
process in SBS 0926+606 A and in Tol 1457-262. All these results reinforce the
hypothesis that interactions with or between dwarf objects is a very important
mechanism in the triggering of massive star formation in starburst galaxies,
specially in dwarf ones. It must be highlighted that only deep and very
detailed observationscan provide clear evidences that these subtle interaction
processes are taking place.
