The complex gas kinematics in the nucleus of the Seyfert 2 galaxy NGC 1386 : rotation, outflows, and inflows

Abstract

We present optical integral field spectroscopy of the circum-nuclear gas of the Seyfert 2 galaxy NGC 1386. The data cover the central 7″ × 9″ (530 × 680 pc) at a spatial resolution of 0″. 9 (68 pc), and the spectral range 5700–7000 Å at a resolution of 66 km s−1. The line emission is dominated by a bright central component, with two lobes extending ≈3″ north and south of the nucleus. We identify three main kinematic components. The first has low velocity dispersion ( ¯ σ ≈ 90 km s−1), extends over the whole field of view, and has a velocity field consistent with gas rotating in the galaxy disk. We interpret the lobes as resulting from photoionization of disk gas in regions where the active galactic nucleus radiation cones intercept the disk. The second has higher velocity dispersion ( ¯ σ ≈ 200 km s−1) and is observed in the inner 150 pc around the continuum peak. This component is double peaked, with redshifted and blueshifted components separated by ≈500 km s−1. Together with previous Hubble Space Telescope imaging, these features suggest the presence of a bipolar outflow for which we estimate a mass outflow rate of M˙ ≳ 0.1 M⊙ yr−1. The third component is revealed by velocity residuals associated with enhanced velocity dispersion and suggests that outflow and/or rotation is occurring approximately in the equatorial plane of the torus. A second system of velocity residuals may indicate the presence of streaming motions along dusty spirals in the disk.