VLBA absorption imaging of ionized gas associated with the accretion disk in NGC 1275

Nearly simultaneous VLBA observations of 3C 84, the radio source associated with NGC 1275, have been made at multiple frequencies to study the free-fr ee absorption of the northern, or "counterjet," feature found by Walker, Ro mney, & Benson and by Vermeulen, Readhead, & Backer. Our observations confi rm that the spectra are consistent with free-free absorption and eliminate the possibility that the earlier result was an effect of variability. The n orthern feature is well resolved spatially, so images have been made showin g the distribution of the absorption over a region of about 1.5 pc on a sid e, beginning about 1.5 pc from the presumed location of the central object. That distribution is dominated by a strong decrease with radial distance. The magnitude of the absorption near 2.5 pc projected distance from the cen tral object is consistent with a 10(4) K gas with an emission measure of ab out 5 x 10(8) pc cm(-6). The geometry is consistent with absorption by ioni zed gas associated with an accretion disk. The data provide firm constraint s for models of the outer regions of accretion disks and, perhaps, associat ed winds.