Massive star formation in Wolf-Rayet galaxies: II. Optical spectroscopy results

TL;DR

This study analyzes optical spectroscopy data from 16 Wolf-Rayet starburst galaxies, revealing complex kinematics, metallicity variations, and interaction signatures that suggest galaxy interactions trigger massive star formation.

Contribution

It provides detailed spectroscopic analysis of starburst galaxies, highlighting the role of interactions and mergers in triggering massive star formation, with new insights into their kinematics and chemical properties.

Findings

Evidence of perturbed kinematics in many galaxies

Detection of tidal streams and merging processes

Variations in metallicity and decoupled kinematics

Abstract

(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.