Probing AGN Molecular Torus via Emission, Absorption, and Polarization

A molecular torus in the central parsec scale of active galactic nuclei (AGNs) is a key component that plays important roles of mass accretion, jet collimation, and diversity in appearance depending on viewing angles. Using ALMA and VLBI, we have tackled to unveil physical properties of AGN tori via molecular emission and absorption lines, plasma free-free absorption, and polarimetry. We will present a representative case on the nearby radio galaxy, NGC 1052. This AGN emanates a double-sided jet that casts molecular absorption and plasma free-free absorption features toward the bright synchrotron emission. It also exhibits H2O maser emissions at 22 GHz and 321 GHz, which amplifies background continuum emission through population-inverted H2O molecules in the torus. Abnormally high H13CO-to-H12CO ratio implies high column density one order of magnitude greater than that estimated by X-ray spectroscopy and small covering factor of ~0.17 which is consistent with spatially resolved VLBI opacity map. Sulfur-bearing absorption features indicate jet-torus interaction which generates shocks that heat dust grains. Polarimetry allows us to measure the orientation of magnetic fields inside the molecular torus. In my talk, I'll report highlights of emission and absorption studies on AGNs which would be more productive with WSU.