Feeding versus feedback in AGNs from near-infrared IFU observations : the case of Mrk 79

Abstract

We have mapped the gaseous kinematics and the emission-line flux distributions and ratios from the inner≈680 pc radius of the Seyfert 1 galaxy Mrk 79, using two-dimensional (2D) nearinfrared J- and Kl-band spectra obtained with the Gemini instrument Near-Infrared Integral Field Spectrograph at a spatial resolution of ≈100 pc and velocity resolution of ≈40 km s−1. The molecular hydrogen H2 flux distribution presents two spiral arms extending by ≈700 pc, one to the north and another to the south of the nucleus, with an excitation indicating heating by X-rays from the central source. The low-velocity dispersion (σ ≈ 50 km s−1) and rotation pattern supports a location of the H2 gas in the disc of the galaxy. Blueshifts observed along the spiral arm in the far side of the galaxy and redshifts in the spiral arm in the near side, suggest that the spiral arms are feeding channels of H2 to the inner 200 pc. From channel maps along the H2 λ2.1218 μm emission-line profile we estimate a mass inflow rate of ˙MH2 ≈ 4 × 10−3M yr−1, which is one order of magnitude smaller than the mass accretion rate necessary to power the active galactic nucleus (AGN) of Mrk 79. The emission from the ionized gas (traced by Paβ and [Fe II] λ1.2570 μm emission lines) is correlated with the radio jet and with the narrow-band [O III] flux distribution. Its kinematics shows both rotation and outflows to the north and south of the nucleus. The ionized gas mass outflow rate through a cross-section with radius ≈320 pc located at a distance of ≈455 pc from the nucleus is ˙M out ≈ 3.5M yr−1, which is much larger than the AGN mass accretion rate, indicating that most of the outflowing gas originates in the interstellar medium surrounding the galaxy nucleus, which is pushed away by a nuclear jet.