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9.7. High-resolution 22 GHz continuum observations of NGC 4258

Implications for Advection-Dominated Accretion

Published online by Cambridge University Press:  25 May 2016

J.R. Herrnstein
J.R. Herrnstein*
Affiliation:
National Radio Astronomy Observatory, PO Box 0, Socorro NM, 87801

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VLBA observations of the water megamaser in NGC 4258 reveal an extremely thin, nearly edge-on, slightly warped disk in Keplerian rotation around a 3.5 ± 0.1 × 107M⊙ central mass (Miyoshi et al. 1995). The masers extend from 0.13-0.26 pc (assuming a distance of 6.4 Mpc), and provide an unusual opportunity to probe active galactic nuclei (AGN) accretion on sub-parsec scales and in a system where the mass of the central engine and the geometry of the outer accretion disk are known with precision. Here, I discuss new 22 GHz, VLBA continuum observations of NGC 4258 in the context of advection-dominated accretion models. A more detailed discussion is in preparation (Herrnstein et al. 1998).

Type
Part III. Black Holes and Central Activity
Information
Symposium - International Astronomical Union , Volume 184: The Central Regions of the Galaxy and Galaxies , 1998 , pp. 395 - 396
Copyright
Copyright © Kluwer 1998 

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