IFU observations of luminous type II AGN - I. Evidence for ubiquitous winds

We present observations of 17 luminous (log(L_{[O III]}/L_⊙) > 8.7) local (z < 0.11) type II AGN. Our aim is to investigate the prevalence and nature of AGN-driven outflows in these galaxies by combining kinematic and ionization diagnostic information. We use non-parametric methods (e.g.W₈₀, the width containing 80 per cent of the line flux) to assess the line widths in the central regions of our targets. The maximum values of W₈₀ in each galaxy are in the range 400-1600km s^-1, with a mean of 790 ± 90 km s^-1. Such high velocities are strongly suggestive that these AGN are driving ionized outflows. Multi-Gaussian fitting is used to decompose the velocity structure in our galaxies. 14/17 of our targets require three separate kinematic components in the ionized gas in their central regions. The broadest components of these fits have FWHM = 530-2520 km s^-1, with a mean value of 920 ± 50 km s^-1. By simultaneously fitting both the Hβ/[O III] and Hα/[N II] complexes, we construct ionization diagnostic diagrams for each component. 13/17 of our galaxies show a significant (> 95 per cent) correlation between the [NII]/Hα ratio and the velocity dispersion of the gas. Such a correlation is the natural consequence of a contribution to the ionization from shock excitation and we argue that this demonstrates that the outflows from these AGN are directly impacting the surrounding ISM within the galaxies.