Liz Humphreys

Liz Humphreys Colloquium -- Probing inner NGC 4258: Warped, Unstable and Eccentric?

Nearby AGN NGC 4258 displays strong 22 GHz water maser emission, which enables mapping of a circumnuclear disk at the 40 000 Schwarzschild radius level (within 1 pc of the supermassive black hole). In this talk, I will discuss how we have used the masers to investigate the Unified Model for AGN. I will also describe how we have used the masers to make a new, high-accuracy geometric distance measurement to the galaxy. With this measurement, we have re-anchored the extragalactic distance scale of Riess et al. (2011) and obtain a Hubble constant of 72.0 +/- 3.0 km/s/Mpc.