An energetic hot wind from the low-luminosity active galactic nucleus M81*

For most of their lifetime, super-massive black holes (SMBHs) commonly found in galactic nuclei obtain mass from the ambient medium at a rate well below the Eddington limit1, which is mediated by a radiatively inefficient, hot accretion flow2. Both theory and numerical simulations predict that a strong wind must exist in such hot accretion flows3–6. The wind is of special interest not only because it is an indispensable ingredient of accretion but also, perhaps more importantly, because it is believed to play a crucial role in the evolution of the host galaxy via the so-called kinetic mode active galactic nucleus feedback7,8. Observational evidence for this wind, however, remains scarce and indirect9–12. Here we report the detection of a hot outflow from the low-luminosity active galactic nucleus in M81, based on Chandra high-resolution X-ray spectroscopy. The outflow is evidenced by a pair of Fe xxvi Lyα lines redshifted and blueshifted at a bulk line-of-sight velocity of ±2.8 × 103 km s−1 and a high line ratio of Fe xxvi Lyα to Fe xxv Kα implying a plasma temperature of 1.3 × 108 K. This high-velocity, hot plasma cannot be produced by stellar activity or the accretion inflow onto the SMBH. Our magnetohydrodynamical simulations show that, instead, it is naturally explained by a wind from the hot accretion flow, propagating out to ≳106 times the gravitational radius of the SMBH. The kinetic energy and momentum of this wind can significantly affect the evolution of the circumnuclear environment and beyond. Chandra X-ray spectroscopy reveals a 108 K plasma outflow in the low-luminosity active galactic nucleus M81. Magnetohydrodynamical simulations show this energetic wind to originate from a hot accretion flow and impact its host galaxy.