Kinetic and radiative power from optically thin accretion flows. Issue 2 (2nd March 2017)

• Record Type: Journal Article
• Authors: Sądowski, Aleksander; Gaspari, Massimo
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 468:Issue 2(2017)
• Page Start: 1398
• Page End: 1404
• Publication Date: 2017-03-02
• Subjects: accretion, accretion discs -- black hole physics -- relativistic processes -- methods: numerical; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stx543
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We perform a set of general relativistic, radiative, magneto-hydrodynamical simulations (GR-RMHD) to study the transition from radiatively inefficient to efficient state of accretion on a non-rotating black hole. We study ion to electron temperature ratios ranging from T i / T e = 10 to 100, and simulate flows corresponding to accretion rates as low as $10^{-6}\dot{M}_{\rm Edd}$, and as high as $10^{-2}\dot{M}_{\rm Edd}$ . We have found that the radiative output of accretion flows increases with accretion rate, and that the transition occurs earlier for hotter electrons (lower T i / T e ratio). At the same time, the mechanical efficiency hardly changes and accounts to ≈3 per cent of the accreted rest mass energy flux, even at the highest simulated accretion rates. This is particularly important for the mechanical active galactic nuclei (AGN) feedback regulating massive galaxies, groups and clusters. Comparison with recent observations of radiative and mechanical AGN luminosities suggests that the ion to electron temperature ratio in the inner, collisionless accretion flow should fall within 10 < T i / T e < 30, i.e. the electron temperature should be several percent of the ion temperature.