Spatially resolved observations of outflows in the radio loud AGN of UGC 8782

Abstract

We use optical integral field spectroscopy (IFU) to study the gas emission structure and kinematics in the inner 3.4 × 4.9 kpc2 region of the galaxy UGC 8782 (3C 293), host of a radio loud active galactic nucleus (AGN). The observations were performed with the Gemini-North multi-object spectrograph (GMOS)-IFU on the Gemini North telescope, resulting in a spatial resolution of ∼725 pc at the distance of the galaxy. While the stars present ordered rotation following the orientation of the large-scale disc, the gas shows a disturbed kinematics. The emission-line profiles present two kinematic components: a narrow (σ ≲ 200 km s−1) component associated with the gas in the disc of the galaxy and a broad (σ ≳ 200 km s−1) component produced by gas outflows. Emission-line ratio diagrams indicate that the gas in the disc is excited by the AGN radiation field, while the emission of the outflow includes additional contribution of shock excitation due to the interaction of the radio jet with the environment gas. Deviations from pure rotation, of up to 30 km s−1, are observed in the disc component and likely produced by a previous merger event. The broad component is blueshifted by ∼150–500 km s−1 relative to the systemic velocity of the galaxy in all locations. We construct radial profiles of the mass outflow rate and kinetic power of the ionized gas outflows, which have the maximum values at ∼1 kpc from the nucleus with peak values of M˙out,ΔR=0.5±0.1 M⊙ yr−1 and K˙out,ΔR=(6.8±1.1)×1041 erg s−1. The kinetic coupling efficiency of these outflows are in the range of 1–3 per cent, indicating that they could be powerful enough to affect the star formation in the host galaxy as predicted by theoretical simulations.