An energetic hot wind from the low-luminosity active galactic nucleus M81*
Abstract
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.
- Publication:
-
Nature Astronomy
- Pub Date:
- July 2021
- DOI:
- 10.1038/s41550-021-01394-0
- arXiv:
- arXiv:2106.04041
- Bibcode:
- 2021NatAs...5..928S
- Keywords:
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- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 31 pages, 10 figures