Jet–torus interaction revealed by subparsec SO absorption in NGC 1052

Abstract We report the first $\lambda$2-mm very long baseline interferometry (VLBI) observations of the radio galaxy NGC 1052, conducted with the Korean VLBI Network using a wide-band recording mode. Leveraging the wide bandwidth covering a velocity range at 2300 km s−1, we successfully detect broad (${>}700$ km s−1) multicomponent SO $J_N = 3_3\!-\!2_2$ absorption against the subparsec-scale continuum structure. The absorption profile consists of both redshifted and blueshifted components, including a newly identified blueshifted feature at $-412$ km s−1 relative to the systemic velocity. Significant SO absorption is confined to the central components, with no substantial detection toward the outer jet components. This constrains the location of SO gas to a compact region smaller than 0.45 pc in the subparsec vicinity of the supermassive black hole (SMBH). Our results support the scenario in which SO molecules are evaporated through shock heating caused by jet–torus interaction. The SO gas clumps are likely driven outward by the jet, with some returning toward the SMBH as inflowing material. Comparison with 321 GHz H2O masers reveals partial similarities in spatial distribution and radial velocity, suggesting that the jet–torus interaction may also trigger the excitation of H2O masers.