Outflowing gas in a compact ionization cone in the Seyfert 2 galaxy ESO 153-G20

Abstract

We present two-dimensional ionized gas and stellar kinematics in the inner 1.4 × 1.9 kpc2 of the Seyfert 2 galaxy ESO 153-G20 obtained with the Gemini-South/Gemini multi-object spectrograph integral field unit (GMOS-IFU) at a spatial resolution of ∼250 pc and spectral resolution of 36 kms-1. Strong [O III], Hα, [NII] and [S II] emission lines are detected over the entire field of view. The stellar kinematics trace circular rotation with a projected velocity amplitude of ±96 km s-1, a kinematic major axis in position angle of 11°, and an average velocity dispersion of 123 km s-1. To analyse the gas kinematics, we used aperture spectra, position-velocity diagrams and single/doubleGaussian fits to the emission lines.All lines show two clear kinematic components: a rotating component that follows the stellar kinematics, and a larger-dispersion component, close to the systemic velocity (from which most of the [OIII] emission comes), mainly detected to the south-west. We interpret this second component as gas outflowing at∼400 km s-1 in a compact (300 pc) ionization cone with a half-opening angle ≤40°. The counter-cone is probably obscured behind a dust lane. We estimate a mass outflow rate of 1.1 M yr-1, 200 times larger than the estimated accretion rate on to the supermassive black hole, and a kinetic to radiative power ratio of 1.7 × 10-3. Bar-induced perturbations probably explain the remaining disturbances observed in the velocity field of the rotating gas component.