Recent Star Formation in Galaxies

Abstract

In recent years the study of starburst galaxies has become a very popular subject because of their intimate connection with the global star formation history of the Universe. Current estimates of the star formation rate of the Universe have been interpreted on the basis of our understanding of local analogous galaxies, in particular through UV continuum and optical line emission. On the mean time, recent observations in the IR/mm have revealed that dusty star burst galaxies constitute a major cosmological component during the past epochs of the universe. In spite of the short duration, the transient IR- active phases of these luminous and ultra luminous IR galaxies (LIRGs and ULIRGs) are responsible for a large fraction of the energy emission and metal production at high redshifts. On one side, because of their transient nature, it is of paramount importance to delineate their recent star formation history with the highest possible accuracy. On the other, these IR phases are characterized by a very complex distribution of stars and the dusty interstellar medium (ISM), and it has become clear that the evaluation of dust extinction and star formation is impossible based on optical-UV data only. We review here some of the methods adopted for reconstructing the recent star formation in such galaxies, focusing on two main aspects, namely the degeneracy induced by age-selective absorption in the UV-optical-near infrared wavelength range and the possibility of using the far-infrared to radio correlation to investigate on the early stages of the star-burst phenomenon.