Integral-Field Spectroscopy of the Centaurus A Nucleus

Abstract

We report integral-field spectroscopic observations with the Cambridge Infra-Red Panoramic Survey Spectrograph (CIRPASS) mounted on the GEMINI South telescope of the nucleus of the nearby elliptical NGC 5128 (Centaurus A). We detect 2-dimensional distributions of the following emission-lines: [P II], [Fe II] and Paschen β and extract spatially resolved 2D kinematics of Paβ and [Fe II] emission- lines only. The kinematics of the two emission-lines are similar, but the Paβvelocity gradient is steeper in the centre while the velocity dispersion is low everywhere. Assuming simple disk geometry we estimate the mass of the central black hole. We obtain M_• = 8.25+2.25-4.25 × 107 M⊙, for PA = -3ˆ and i=25ˆ, excluding the M_• - σ relation prediction at a 3σ confidence level, which is in good agreement with previous studies.