Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers

The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei\nof Seyfert galaxies is a well established observational fact. This material is systematically\noutflowing and shows a large range in parameters. However, its actual nature and dynamics\nare still not clear. In order to gain insights into these important issues we performed a literature\nsearch for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type\n1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in\nthe same sample. The fraction of sources with WAs is >60 per cent, consistent with previous\nstudies. The fraction of sources with UFOs is >34 per cent, >67 per cent of which also\nshow WAs. The large dynamic range obtained when considering all the absorbers together,\nspanning several orders of magnitude in ionization, column, velocity and distance allows us,\nfor the first time, to investigate general relations among them. In particular, we find significant\ncorrelations indicating that the closer the absorber is to the central black hole, the higher the\nionization, column, outflow velocity and consequently the mechanical power. In all the cases,\nthe absorbers continuously populate the whole parameter space, with the WAs and the UFOs\nlying always at the two ends of the distribution. These evidence strongly suggest that these\nabsorbers, often considered of different types, could actually represent parts of a single large-scale\nstratified outflow observed at different locations from the black hole. The UFOs are likely\nlaunched from the inner accretion disc and the WAs at larger distances, such as the outer disc\nand/or torus. We argue that the observed parameters and correlations are, to date, consistent\nwith both radiation pressure through Compton scattering and magnetohydrodynamic processes\ncontributing to the outflow acceleration, the latter playing a major role. Most of the absorbers,\nespecially the UFOs, show a sufficiently high mechanical power (at least approx 0.5 per cent of the\nbolometric luminosity) to provide a significant contribution to active galactic nuclei (AGN)\nfeedback and thus to the evolution of the host galaxy. In this regard, we find possible evidence\nfor the interaction of the AGN wind with the surrounding environment on large scales.