High-angular-resolution ALMA imaging of the inhomogeneous dynamical atmosphere of the asymptotic giant branch star W Hya. SiO, H2O, SO2, SO, HCN, AlO, AlOH, TiO, TiO2, and OH lines

We present high-angular-resolution imaging of the asymptotic giant branch star W Hya with the Atacama Large Millimeter/submillimeter Array (ALMA) to probe the dynamics and chemistry in the atmosphere and inner wind. W Hya was observed with the longest baselines of ALMA at 250--268 GHz with an angular resolution of ∼17times20 mas. ALMA's high angular resolution allowed us to resolve the stellar disk of W Hya along with clumpy, irregularly shaped emission extending to ∼100 mas. This emission includes a plume in the north-northwest, a tail in the south-southwest, and the extended atmosphere elongated in the east-northeast--west-southwest direction, with semimajor and semiminor axes of ∼70 and 40 mas (∼3.4 and 1.9 R_⋆ ), respectively. We identified 57 lines, which include SiO H_2O SO_2 SO, HCN, AlO, AlOH, TiO TiO_2 OH, and some of their isotopologues, with about half of them being in vibrationally excited states. The molecular line images show spatially inhomogeneous molecular formation. Our ALMA data taken at phase 0.53 (minimum light) indicate global, accelerating infall within ∼75 mas (3.6 R_⋆ ) but also outflow at up to ∼10 km s^-1 in deeper layers. While 38 of the detected lines appear in absorption against the continuum stellar disk as expected, we detect nonthermal emission on top of the continuum over the stellar disk in 19 lines, including SiO H_2O SO_2 and AlO. The emission of the SiO, AlO, TiO TiO_2 SO, and SO_2 lines coincides well with the clumpy dust cloud distribution obtained from contemporaneous visible polarimetric imaging in addition to H_2O reported in our previous work. This lends support to the idea that SiO H_2O and AlO are directly involved in grain nucleation. The overlap of SO/ SO_2 (possibly also TiO/ TiO_2 ) with the dust clouds suggests the formation of these molecules and dust behind shocks induced by pulsation and/or convection. We detect HCN emission close to the star, down to ∼30 mas (∼1.4 R_⋆ ), which is consistent with shock-induced chemistry.