Spectral Energy Distribution of Hyper-Luminous Infrared Galaxies

Abstract

The relationship between star formation and super-massive black hole growth is central to our understanding of galaxy formation and evolution. Hyper-Luminous Infrared Galaxies (HLIRGs) are unique laboratories to investigate the starburst-AGN connection, since they exhibit extreme star formation rates, and most of them show evidence of harboring powerful AGN. We have performed an X-ray spectral study of a sample of HLIRGs observed with XMM-Newton, finding that the X-ray emission of most of these sources is dominated by AGN activity. To improve our estimate of the relative contribution of the AGN and starburst (SB) emission to its total bolometric output, we have built multi-wavelength (from radio to X-rays) spectral energy distributions (SED) for these HLIRGs, and we have fitted standard AGN and SB templates to these SEDs. We have found that most of our HLIRGs need an AGN template to model its SED, and this component dominates the bolometric output. We also have found that our sources classified as type 1 AGN are better modeled using a luminosity-dependent template. Extending the SED to the X-ray bands places better constraints on the relative contribution of the AGN and SB with respect to using only IR/sub-mm data.