  We solve for the velocity fields of momentum-conserving supershells driven by
feedback from supermassive black holes or nuclear star clusters (central
massive objects: CMOs). We treat, for the first time, the case of CMOs embedded
in gaseous protogalaxies with non-isothermal dark matter haloes having peaked
circular-speed profiles. We find the CMO mass that is sufficient to drive any
shell to escape any such halo. In the limit of large halo mass, relevant to
real galaxies, this critical CMO mass depends only on the peak circular speed
in the halo, scaling as M_crit \propto V_c,pk^4.
