Star-forming accretion flows and the low-luminosity nuclei of giant elliptical galaxies

摘要: The luminosities of the centres nearby elliptical galaxies are very low compared to models thin disc accretion on their black holes at Bondi rate, typically a few hundredths tenths solar mass per year. This has motivated inefficiently radiated that invoke weak electron‐ion thermal coupling, and/or inhibited rates due convection or outflows. Here we point out that, even if such processes operating, significant fraction accreting gas is prevented from reaching central hole because it condenses into stars in gravitationally unstable disc. Star formation occurs inside radius (typically ∼100 pc giant ellipticals), but still relatively far terms Schwarzschild radii. depletes and heats disc, eventually leading marginally stable, much reduced, flow hole. We predict presence cold (∼100 K), dusty discs, containing clustered Hα emission occasional Type II supernovae, both resulting massive stars. accounts for several features M87 system: traced by emission, observed scales about 100 pc, with reminiscent spiral arms dust lanes; star rate inferred intensity consistent system. may therefore help suppress engines ellipticals. also discuss some implications fuelling Galactic Centre quasars. Ke yw ords: accretion, discs ‐ physics stars: galaxies: active lenticular, cD individual: M87.