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New Astronomy Reviews



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The nearby (41 Mpc) FR-I radio galaxy NGC 4261 contains a pair of symmetric kpc-scale jets, emerging from the vicinity of a 5×108 M black hole. We present new VLBA observations of NGC 4261 at 22 and 43 GHz which we combine with previous observations at 1.6 and 8.4 GHz. We find that the orientation of the radio jet axis is the same on pc and kpc scales, indicating that the spin axis of the inner accretion disk and black hole has remained unchanged for at least 106 (and more likely >107) years. This suggests that a single merger event may be responsible for the supply of gas in the nucleus of NGC 4261. We also use our VLBA images to probe the structure of the accretion disk on sub-parsec scales through free-free absorption of synchrotron emission from the base of symmetric radio jets.