The X-ray view of winds in Active Galactic Nuclei

Our X-ray view of winds in Active Galactic Nuclei (AGN) has significantly improved in recent years. In this talk I will briefly review some of the main observational results in this field. For instance, supporting evidences for highly ionized, high column, ultra-fast outflows (UFOs) have been reported through the detection of blue-shifted Fe K absorption lines with velocities up to ~0.1-0.3c. Their overall characteristics suggest a direct identification with winds ejected from the inner accretion disk. High signal-to-noise soft X-ray observations of the more "classical" warm absorbers (WAs) showed that they are indeed composed of several layers of outflowing gas, suggesting that some form of ionized absorption could actually be ubiquitous in AGNs. Moreover, these winds have been observed in both radio-quiet and radio-loud AGNs, the UFOs also showing a tentative connection with prominent disk-jet ejection cycles. Significant correlations between the parameters of the WAs and UFOs have been reported, suggesting their possible unification as a single, large-scale stratified outflow observed at different locations along the line of sight, from the vicinity of the central black hole up to the outskirts of the AGN host galaxy. Their detailed acceleration mechanism(s) are still debated, but observations and theoretical results favor a combination of radiation pressure and/or MHD processes. The deposition of mass and energy of these winds, and especially the UFOs, in the AGN host galaxy can be substantial and, indeed, they may represent the long sought-after agent mediating the "quasar mode" feedback. Finally, I will show simulations of the improvements in these studies that will come from the unprecedented Fe K energy resolution and sensitivity of the calorimeters onboard the upcoming ASTRO-H mission and the future Athena+ observatory.

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