X-raying winds in distant quasars: The first high-redshift wind duty cycle

Aims: Theoretical models of wind-driven feedback from active galactic nuclei (AGN) often identify ultra-fast outflows as being the main agent in the generation of galaxy-sized outflows, which are possibly the main actors in establishing so-called AGN-galaxy co-evolution. Ultra-fast outflows are well characterized in local AGN but much less is known in quasars at the cosmic time when star formation and AGN activity peaked (z ≃ 1-3). It is therefore necessary to search for evidence of ultra-fast outflows in high-z sources to test wind-driven AGN feedback models.
Methods: Here we present a study of Q2237+030, the Einstein Cross, a quadruply-imaged radio-quiet lensed quasar located at z = 1.695. We performed a systematic and comprehensive temporally and spatially resolved X-ray spectral analysis of all the available Chandra and XMM-Newton data (as of September 2019).
Results: We find clear evidence for spectral variability, possibly due to absorption column density (or covering fraction) variability intrinsic to the source. For the first time in this quasar, we detect a fast X-ray wind outflowing at v_out ≃ 0.1c that would be powerful enough (Ė_kin ≃ 0.1 L_bol) to significantly affect the evolution of the host galaxy. We report also on the possible presence of an even faster component of the wind (v_out ∼ 0.5c). For the first time in a high-z quasar, given the large sample and long time interval spanned by the analyzed X-ray data, we are able to roughly estimate the wind duty cycle as ≃0.46 (0.31) at 90% (95%) confidence level. Finally, we also confirm the presence of a Fe Kα emission line with variable energy, which we discuss in the light of microlensing effects as well as considering our findings on the source.