SWIFT/BAT AGN2 reveal broad emission lines in the NIR: the first virial measure of their black hole masses

In the last decade, using single epoch (SE) virial based techniques in the optical band, it has been possible to measure the Active Galactic Nuclei (AGN) black hole (BH) mass on large type 1 AGN (AGN1) samples and therefore to estimate the supermassive BH mass function (SMBHMF). However these measurements cannot be applied on those obscured type 2 (AGN2) where the nuclear component does not dominate in the optical. The lack of knowledge of BH masses for AGN2 may limit our studies and understanding of AGN/galaxy evolution. We here present new results from a systematic study carried out using near infrared (NIR) spectroscopy (ISAAC and Xshooter at VLT and LUCI at LBT) of 41 AGN2, drawn from the SWIFT/BAT 70-month hard X-ray survey. We derived a new virial relation able to estimate the BH mass using the broad component of the Paβ emission line and the AGN hard X-ray luminosity. We have revealed the Paβ broad component in 13 out of 41 AGN2. Thanks to the above relation, we have been able to directly measure their BH masses, finding that AGN2 show, on average, low BH masses (<107 M), 0.8 dex smaller than those of AGN1 with the same intrinsic hard X-ray luminosity.