VLBA Continuum Observations of NGC 4258: Constraints on an Advection-Dominated Accretion Flow

J. R. Herrnstein, L. J. Greenhill, J. M. Moran +4

We report a 3 sigma upper limit of 220 microJanskys on any 22-GHz continuum emission coincident with the central engine in NGC 4258. If NGC 4258 is powered by an advection-dominate…