The origin of optical emission from super-Eddington accreting Active Galactic Nuclei: The case of Ton S 180
Résumé
Self-gravitating accretion discs have only been studied in a few nearby objects using maser spots at the parsec-scale. We find a new spectral window for observing the self-gravitating accretion disc in super-Eddington accreting Active Galactic Nuclei (AGNs). This window is determined by calculating the outermost radius (rsg) of a non self-gravitating disc and the corresponding emission wavelength (lambdasg) as a function of various disc parameters. We find that lambdasg reaches ˜4000 Å for alpha=0.1, when M&sun; ≳ 70 (MBH / 107 M&sun;)-1 LEdd/c2 (where &alpha,; M&sun;, MBH and LEdd are, respectively, the viscosity parameter, gas accretion rate onto the central black hole (BH), the BH mass and the Eddington luminosity). Moreover, lambdasg is as small as ˜ 1500 Å for alpha =0.001, which is the smallest alpha case in this study. Therefore, the window for observing the self-gravitating part of an AGN accretion disc is from ˜ 2 mum to lambdasg. Incidentally, rsg can be less than the photon trapping radius for M&sun; ≳ 103.3 LEdd/c2. Namely, a self-gravitating, optically-thick, advection-dominated accretion disc is expected to appear in the extremely high accretion rate regime.
Domaines
Astrophysique [astro-ph]
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