Angel Lopez-Sanchez (CSIRO ATNF)

Massive star formation in dwarf Wolf-Rayet galaxies - Angel Lopez-Sanchez colloquium

ATNF Marsfield Lecture Theatre

Abstract

In this colloquium I present the main results of my PhD Thesis, in which a detailed morphological, photometrical and spectroscopical analysis of a sample of 20 Wolf-Rayet (WR) galaxies was realized. WR galaxies are a subtype of H II galaxies whose integrated spectra show broad emission lines attributed to WR stars, indicating the presence of an important population of massive stars and the youth of the starburst. The main aims are the study of the star formation and O and WR stellar populations in these galaxies and the role that interactions between low surface companion objects could have in the triggering mechanism of the bursts.

Deep and high spatial resolution imagery in optical and near-infrared (NIR) broad band and narrow-band (H_alpha and continuum) filters have been used to study the morphology of the stellar and ionized gas of each galaxy, its surroundings and possible faint companion objects. The ionizing stars content and the age of the recent star formation bursts and the old stellar underlying population are also analyzed. Long slit and echelle spectroscopy have been used to locate and quantify the massive stars within the galaxies, as well as to study the physical conditions, chemical abundances and kinematics of the ionized gas, disentangling the tidal/pre-existing nature of the companion objects surrounding the main galaxies. The optical/NIR observations are completed with X-ray, far-infrared and radio (H I and continuum) data extracted from the literature in order to achieve a global vision of the star formation activity and evolution of each galaxy.

General results involving all the galaxy sample and considering all the multiwavelength data are presented. I conclude that the majority of the analyzed galaxies (16 up to 20, ~80% of the objects) show clear interaction features, confirming the hypothesis that interaction with or between dwarf objects trigger the star formation activity in Wolf-Rayet galaxies.