Most of the active star formation in our local universe takes place in what we call “normal” spirals: disk galaxies with the bulk of their emission at ultraviolet and optical wavebands. Extremely dusty galaxies, with an enhanced emission at infrared wavelengths are pretty much extremely rare “freaks” in today’s universe. However, these so-called ultra-luminous infrared galaxies (ULIRGs) dominate the co-moving energy density at higher redshifts (z>2). Many of these have been identified by the detection of their thermal dust emission at millimeter (mm) and sub-mm wavelengths. Detailed ground-based follow-up of these sub-mm galaxies (SMGs) in the optical/near-IR and radio, as well as space-based studies with Chandra, HST, Spitzer and Herschel telescopes have revealed intricate morphologies reminiscent of major galaxy mergers, and the predominance of active galactic nuclei (AGN), establishing that star formation and the growth of super-massive black hole growth coexist in these objects. With colossal IR luminosities that translate into unusually high SFRs (~100-1000 MSun /yr), SMGs are extreme starbursting galaxies that could build the stellar bulk of a massive galaxy in under a few hundred million years. These findings suggest that the submm phase may represent a dust-obscured pre-quasar period in the evolutionary scenario that leads to the formation of today’s massive ellipticals. I will provide a review on the subject of dusty galaxies in the distant universe and discuss their role within the formation scenario of massive passive galaxies. I will also share some of my ongoing work to study the environments of these systems, as tracers of protoclusters in the distant universe.
