The first detection of near-infrared CN bands in active galactic nuclei:: Signature of star formation

We present the first detection of the near-infrared CN absorption band in the nuclear spectra of active galactic nuclei (AGNs). This feature is a recent star formation tracer, being particularly strong in carbon stars. The equivalent width of the CN line correlates with that of the CO at 2.3 mu m as expected in stellar populations (SPs) with ages between similar to 0.2 and similar to 2 Gyr. The presence of the 1.1 mu m CN band in the spectra of the sources is taken as unambiguous evidence of the presence of young/intermediate SPs close to the central source of the AGNs. Near-infrared bands can be powerful age indicators for star formation connected to AGNs, the understanding of which is crucial in the context of galaxy formation and AGN feedback.