Intergalactic Star Formation around NGC 5291
Résumé
I will present a project aimed at characterizing systematically the intergalactic star formation taking place in gas expelled from galaxies into the IGM by tidal forces during close encounters. A part of the ejected gas collapses to form new stars and depending on dynamical conditions may even form new galaxies called "tidal dwarf galaxies". Those objects are chemically similar to star formation regions in spiral disks (roughly solar metallicity) but are dynamically similar to young dwarf galaxies. How star formation (star formation rate, initial mass function, age, extinction, dust properties, etc.) proceeds in such a particular environment, far away from the parent stellar disks, has yet not been studied in details. In order to get a better understanding of this mode of star formation, we performed a multi-wavelength study combining radio HI (VLA), mid-infrared (Spitzer), near-infrared and optical (ground based), and ultraviolet (Galex) data. We compared the properties of the intergalactic star forming regions (extinction, age, metallicity, dust properties) with those of several samples of dwarf galaxies and individual HII regions in different galaxies. Coupling those observations with spectra modelized using evolutive synthesis codes will allow us to determine precise measurements of the star formation rates and to obtain some constraints on the initial mass function.