High energy emission from starburst galaxies

The star formation (SF) can be regarded as an engine powering the light emission of spiral galaxies at several wavelengths. SF activity also plays a significant role in the evolution of galaxies. In this thesis we focus on the X-ray emission from processes related to star formation. Several kinds of sources concur to X-ray emission, X-ray binaries and hot plasma being the most important. We begin with a review of the infrared, radio and X-ray emission from star forming galaxies. In the second chapter we explore the quantitative relationships between the total X-ray, radio and infrared luminosities for a sample of 23 star forming galaxies. It is found that linear correlations hold between the luminosities in the above bands. In the third chapter we show, by analyzing a sample of 11 high redshift galaxies in the Hubble Deep Field, that the linear correlations may be extended up to z~1. In the fourth chapter we turn to an analysis of the luminosity function and number counts of star forming galaxies; we show that the number density of normal galaxies at faint X-ray fluxes (10^-17 -- 10^-15 erg/s/cm2) is very well defined. The fifth chapter offers a first insight into a different aspect of galaxy evolution, i.e. whether is it possible to determine the metallicity enhancements in a starburst episode. An interesting, yet problematic, picture of metal enrichment of the interstellar matter arises from an analysis of the X-ray and near infrared spectra of M82. Finally, a summary is offered of the work here described.