The dense plasma torus around the nucleus of an active galaxy NGC 1052

A subparsec-scale dense plasma torus around an active galactic nucleus is u nveiled. We report on very-long baseline interferometry (VLBI) observations at 2.3, 8.4, and 15.4 GHz towards the active galaxy NGC 1052. The convex s pectra of the double-sided jets and the nucleus imply that synchrotron emis sion is obscured through free-free absorption (FFA) by the foreground cold dense plasma. A trichromatic image was produced to illustrate the distribut ion of the FFA opacity. We found a central condensation of the plasma which covers about 0.1 pc and 0.7 pc of the approaching and receding jets, respe ctively. A simple explanation for the asymmetric distribution is the existe nce of a thick plasma torus perpendicular to the jets. We also found an amb ient FFA absorber, whose density profile can be ascribed to a spherical dis tribution of the isothermal King model. The coexistence of torus-like and s pherical distributions of the plasma suggests a transition from radial accr etion to rotational accretion around the nucleus.