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

Abstract

We present observations of 17 luminous (log(L[O III]/L_Sun) > 8.7) local (z <\n0.11) type II AGN. Our aim is to investigate the prevalence and nature of AGN\ndriven outflows in these galaxies by combining kinematic and ionization\ndiagnostic information. We use non-parametric methods (e.g. W80, the width\ncontaining 80% of the line flux) to assess the line widths in the central\nregions of our targets. The maximum values of W80 in each galaxy are in the\nrange 400 - 1600 km/s, with a mean of 790 +- 90 km/s. Such high velocities are\nstrongly suggestive that these AGN are driving ionized outflows. Multi-Gaussian\nfitting is used to decompose the velocity structure in our galaxies. 14/17 of\nour targets require 3 separate kinematic components in the ionized gas in their\ncentral regions. The broadest components of these fits have FWHM = 530 - 2520\nkm/s, with a mean value of 920 +- 50 km/s. By simultaneously fitting both the\nH{\\beta}/[O III] and H{\\alpha}/[N II] complexes we construct ionization\ndiagnostic diagrams for each component. 13/17 of our galaxies show a\nsignificant (> 95 %) correlation between the [N II]/H{\\alpha} ratio and the\nvelocity dispersion of the gas. Such a correlation is the natural consequence\nof a contribution to the ionization from shock excitation and we argue that\nthis demonstrates that the outflows from these AGN are directly impacting the\nsurrounding ISM within the galaxies.\n