Accretion output relative to galactic binding energy ($E_{\mathrm{rad}}/|W|\sim [\eta /(1-\eta )]\alpha (c/\sigma {)}^2$)

If a hole gains mass $\Delta M_{\mathrm{BH}}$ at constant radiative efficiency $\eta =L/({\dot{M}}_{\mathrm{in}}{c}^2)$, the radiated energy is $\eta \Delta M_{\mathrm{BH}}{c}^2/(1-\eta )$. For negligible seed mass, final hole mass $\alpha M$, and total three-dimensional galaxy dispersion $\sigma$, its ratio to $|W|\simeq M{\sigma }^2$ is $\eta \alpha (c/\sigma {)}^2/(1-\eta )$. The net virial unbinding energy is half $|W|$ when surface terms are negligible.