Gemini Near Infrared Integral Field Spectroscopy of the Narrow-Line Region of ESO428-G14: kinematics, excitation and the role of the radio jet

Abstract

We present 2D gas kinematics and excitation of the inner 300 pc of the Seyfert galaxy ESO428-G14 at a sampling of 14 pc^2, from near-IR spectroscopic observations at R~6000 obtained with the IFU of the Gemini Near-Infrared Spectrograph. From measurements of fluxes and profiles of the emission lines [FeII]lambda1.257, Pa_beta, H_2lambda2.121 and Br_gamma, we construct 2D maps of line intensities and ratios, radial velocities and velocity dispersions. Emission lines "tomography" is provided by velocity slices obtained across the line profiles, which allows the mapping of not only of peak velocities but including also the wings. We compare these maps with a previously published high spatial resolution radio map and find a tight relation between the radio structure and the emission-line flux distributions and kinematics, revealing that the radio-jet plays a fundamental role not only in shaping the NLR but also in the imprint of its kinematics. Blueshifts of up to 400 km/s and velocity dispersions of up to 150 km/s are observed in association with the radio jet at position angle PA=129, which is also the PA of the photometric major axis of the galaxy. The [FeII] shows the largest blueshifts and velocity dispersions and its flux distribution is concentrated along the jet, while the H_2 shows the lowest velocity dispersions and has additional flux contribution from regions beyond the jet. We use the 2D velocity dispersion maps to estimate upper limits to the contribution of the radio jet to the excitation of [FeII] and H_2 which may reach 90% for [FeII] and 80% for H_2 in the jet region. The [FeII]/Pa_beta emission-line ratios and the association of the [FeII] flux distribution and kinematics with the radio structure supports a stronger contribution of the radio jet to the [FeII] excitation than to that of H_2.