Detection of Faint BLR Components in the Starburst/Seyfert Galaxy NGC
  6221 and Measure of the Central BH Mass
  In the last decade, using single epoch virial based techniques in the optical
band, it has been possible to measure the central black hole mass on large AGN1
samples. However these measurements use the width of the broad line region as a
proxy of the virial velocities and are therefore difficult to be carried out on
those obscured (type 2) or low luminosity AGN where the nuclear component does
not dominate in the optical. Here we present the optical and near infrared
spectrum of the starburst/Seyfert galaxy NGC 6221, observed with X-shooter/VLT.
Previous observations of NGC 6221 in the X-ray band show an absorbed (N_H=8.5
+/- 0.4 x 10^21 cm^-2) spectrum typical of a type 2 AGN with luminosity
log(L_14-195 keV) = 42.05 erg/s, while in the optical band its spectrum is
typical of a reddened (A_V=3) starburst. Our deep X-shooter/VLT observations
have allowed us to detect faint broad emission in the H_alpha, HeI and Pa_beta
lines (FWHM ~1400-2300 km/s) confirming previous studies indicating that NGC
6221 is a reddened starburst galaxy which hosts an AGN. We use the measure of
the broad components to provide a first estimate of its central black hole mass
(M_BH = 10^(6.6 +/- 0.3) Msol, lambda_Edd=0.01-0.03), obtained using recently
calibrated virial relations suitable for moderately obscured (N_H<10^24 cm^-2)
AGN.
