Are ultra-luminous galaxies colliding?
(Phys.org) —ltra-luminous infrared galaxies ((ULIRGs) are galaxies whose luminosity exceeds that of a trillion suns, By way of comparison, our Milky Way galaxy has a typical modest luminosity of only about ten billion suns. ULIRGs were discovered by an all-sky infrared survey satellite in the 1980's, and since then the origin(s) of their powerful emission has been widely debated. Extreme infrared activity is known to be associated with interacting galaxies, and optical imaging shows that many ULIRGs are indeed in collision. The two primary known sources of global energy production in galaxies are star formation and accretion activity around a massive black hole in the nucleus (a so-called active galactic nucleus). Both of them produce radiation that heats up the dust. Mergers might result in intense infrared emission.because they help to drive this kind of active star formation.