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R.C. Walker, K.I. Kellermann, V. Dhawan, J.D. Romney, J.M. Benson (NRAO), R.C. Vermeulen (NFRA), W. Alef (MPIfR)
Nearly simultaneous VLBA observations of 3C~84, the radio source in NGC~1275, have been made at several frequencies to study the free-free absorption of the northern, or ``counterjet'', feature found by Walker, Romney, and Benson (1994, Ap. J., 430, L45) and by Vermeulen, Readhead, and Backer (1994, Ap. J., 430, L41). The absorption is probably by ionozed gas associated with the parsec scale accretion disk. The observations confirm that the spectra are consistent with free-free absorption and rule out the possibility that the earlier result was an effect of variability. The northern feature is well resolved spatially, so images have been made showing the distribution of the absorption over a region of about a square parsec. The variations in the absorption are dominated by a strong decrease radially away from the central object.
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