2006ApJ...637L..17R

We present 3-5 µm spectroscopy of the interacting system NGC 6240, revealing the presence of two active galactic nuclei (AGNs). The brightest (southern) nucleus shows up with a starburst-like emission, with a prominent 3.3 µm emission feature. However, the presence of an AGN is revealed by the detection of a broad Brα emission line, with a width of ∼1800 km/s. The spectrum of the faintest (northern) nucleus shows typical AGN features, such as a steep continuum and broad absorption features in the M band. We discuss the physical properties of the dusty absorbers/emitters, and we show that in both nuclei, the AGN is dominant in the 3-5 µm band but that its contribution to the total luminosity is small (a few percent of the starburst emission).