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In The Shadow Of The Accretion Disk: Higher Resolution Imaging Of The Central Parsec In Ngc 4261, B. Glenn Piner, Dayton L. Jones, Ann E. Wehrle, David L. Meier

Physics

The physical conditions in the inner parsec of accretion disks believed to orbit the central black holes in active galactic nuclei can be probed by imaging the absorption (by ionized gas in the disk) of background emission from a radio counterjet. We report high angular resolution VLBI observations of the nearby (~40 Mpc) radio galaxy NGC 4261 that confirm free-free absorption of radio emission from a counterjet by a geometrically thin, nearly edge-on disk at 1.6, 4.8, and 8.4 GHz. The angular width and depth of the absorption appears to increase with decreasing frequency, as expected. We derive an average …