Interstellar medium conditions in starburst galaxies

Abstract

In this thesis I study in detail the conditions of the interstellar medium of a three starburst galaxies that cover a wide range of metallicities and star formation areas. I have shown a strong support for efficient destruction of PAH molecules by UV photons in NGC 5253, independently of variations of metallicity. In a more luminous central starburst galaxy such as M82, the radiation field is about 40 times softer than in NGC 5253 with little spatial variation, and the star formation has been strongly suppressed in the last 5 Myr as a result of feedback effects. On scales larger than a few kiloparsecs, large scale events like galaxy interactions become relevant. From studying Arp 143, I found strong support for the scenario in which a radially expanding, large-scale shock wave from a head-on galaxy-galaxy collision has swept up the interstellar medium and triggered the formation of these clusters. Finally, I investigated the properties of the dust emission in starburst environments. A small fraction of galaxies require a very cold component with T<14 K. Most of these "cold" galaxies are mergers and exhibit a high fraction of stochastically heated very small grains (VSGs). Either a large amount of big, very cold silicate grains in the diffuse ISM, or a significantly higher fraction of VSGs.