|Speaker||Talk Date||Talk Series|
|David Elbaz, CEA Saclay, Service d'Astrophysique||28 April, 2011||Institute of Astronomy Colloquia|
Evidence has been recently gathered suggesting that galaxies in their main star formation episodes follow some scaling laws, somewhat similar to the fundamental plane for early-types. This suggests that behind the complexity of galaxy and star formation, exist some dominant physical processes conducting galaxy evolution, which appear as mostly internal to galaxies. Investigating these processes is a difficult task requiring unbiased galaxy samples with accurate star formation rates, stellar masses,... In this perspective, we will review the latest results obtained with the deepest far-infrared imaging of the Universe in the GOODS fields with the Herschel observatory - GOODS-Herschel. We will show that at all epochs the bulk of star forming galaxies appear to follow a Main Sequence (MS), valid for galaxies of all star formation rates and luminosities, while a fifth of them form stars in a starburst mode (SB). Previous claims for mid-infrared excess galaxies, obscured AGNs and strong evolution of the IR spectral energy distribution of galaxies will be discussed in this framework. Using radio and UV imaging, we will show that starbursts have large projected surface densities of star formation while MS, including most distant ULIRGs, present extended star formation like local normal star forming galaxies. A universal infrared spectral energy distribution will be presented for MS star forming galaxies as well as starbursts. Finally, we will show how these considerations can be used to search for previously unidentified obscured active nuclei.