The double AGN in NGC 6240 revealed through 3-5 micron spectroscopy

摘要

We present 3-5 micron spectroscopy of the interacting system NGC 6240,showing the presence of two active galactic nuclei. The brightest (southern)nucleus shows up with a starburst-like emission, with a prominent 3.3 micronemission feature. However, the presence of an AGN is revealed by the detectionof a broad Br alpha emission line, with a width of ~1,800 km/s. The spectrum ofthe faintest (northern) nucleus shows typical AGN features, such as a steepcontinuum and broad absorption features in the M-band. We discuss the physicalproperties of the dusty absorbers/emitters, and show that in both nuclei theAGN is dominant in the 3-5 micron band, but its contribution to the totalluminosity is small (a few percent of the starburst emission).