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We calculate steady-state, one-dimensional hydrodynamic profiles of hot gasin slowly accreting ("quiescent") galactic nuclei for a range of central blackhole masses $M_{\bullet}$, parametrized gas heating rates, andobservationally-motivated stellar density profiles. Mass is supplied to thecircumnuclear medium by stellar winds, while energy is injected primarily bystellar winds, supernovae, and black hole feedback. Analytic estimates arederived for the stagnation radius (where the radial velocity of the gas passesthrough zero) and the large scale gas inflow rate, $\dot{M}$, as a function of$M_{\bullet}$ and the gas heating efficiency, the latter being related to thestar-formation history. We assess the conditions under which radiativeinstabilities develop in the hydrostatic region near the stagnation radius,both in the case of a single burst of star formation and for the average starformation history predicted by cosmological simulations. By combining a sampleof measured nuclear X-ray luminosities, $L_x$, of nearby quiescent galacticnuclei with our results for $\dot{M}(M_{\bullet})$ we address whether thenuclei are consistent with accreting in a steady-state, thermally-stable mannerfor radiative efficiencies predicted for radiatively inefficiency accretionflows. We find thermally-stable accretion cannot explain the short averagegrowth times of low mass black holes in the local Universe, which must insteadresult from gas being fed in from large radii, due either to gas inflows orthermal instabilities acting on larger, galactic scales. Our results haveimplications for attempts to constrain the occupation fraction of SMBHs in lowmass galaxies using the mean $L_x-M_{\bullet}$ correlation, as well as thepredicted diversity of the circumnuclear densities encountered by relativisticoutflows from tidal disruption events.

Circumnuclear Media of Quiescent Supermassive Black Holes