| Title | 3-5 μm Spectroscopy of Obscured AGNs in ULIRGs |
| Authors | Sani, E.; Risaliti, G.; Salvati, M.; Maiolino, R.; Marconi, A.; Berta, S.; Braito, V.; Della Ceca, R.; Franceschini, A. |
| Bibcode | 2008ApJ...675...96S Search ADS ↗ |
| Abstract | We present the results of infrared L-band (3-4 μm) and M-band (4-5 μm) Very Large Telescope (VLT) ISAAC spectroscopy of five bright ultraluminous infrared galaxies (ULIRGs) hosting an AGN. From our analysis we distinguish two types of sources: ULIRGs in which the AGN is unobscured (with a flat continuum and no absorption features at 3.4 and 4.6 μm), and those with highly obscured AGNs (with a steep, reddened continuum and absorption features due to hydrocarbons and CO). Starburst activity is also present in all of the sources, as inferred from the 3.3 μm PAH emission line. A strong correlation is found between continuum slope and CO optical depth, which suggests that deep carbon monoxide absorption is a common feature of highly obscured ULIRG AGNs. Finally, we show that the AGN dominates the 3-4 μm emission, even if its contribution to the bolometric luminosity is small. Based on observations collected at the European Southern Observatory, Chile (proposals ESO 73.B-0574, 79.B-0052). |
| Objects | 7 Objects Search NED ↙ |
