摘要：Aims.We study the spatial distribution and kinematics of water emission in a ~8 × 8 pc2region of the Galactic center (GC) that covers the main molecular features around the supermassive black hole Sagittarius A*(Sgr A*). We also analyze the water excitation to derive the physical conditions and water abundances in the circumnuclear disk (CND) and the “quiescent clouds”.Methods.We presented the integrated line intensity maps of the ortho 110− 101, and para 202− 111and 111− 000water transitions observed using the On the Fly mapping mode with the Heterodyne Instrument for the Far Infrared (HIFI) on boardHerschel. To study the water excitation, we used HIFI observations of the ground state ortho and para H218O transitions toward three selected positions in the vicinity of Sgr A*. In our study, we also used dust continuum measurements of the CND, obtained with the Spectral and Photometric Imaging REceiver (SPIRE) instrument. Using a non-local thermodynamical equilibrium (LTE) radiative transfer code, the water line profiles and dust continuum were modeled, deriving H2O abundances (XH2O), turbulent velocities (Vt), and dust temperatures (Td). We also used a rotating ring model to reproduce the CND kinematics represented by the position velocity (PV) diagram derived from para 202− 111H2O lines.Results.In our H2O maps we identify the emission associated with known features around Sgr A*: CND, the Western Streamer, and the 20 and 50 km s−1clouds. The ground-state ortho water maps show absorption structures in the velocity range of [−220,10] km s−1associated with foreground sources. The PV diagram reveals that the 202− 111H2O emission traces the CND also observed in other high-dipole molecules such as SiO, HCN, and CN. Using the non-LTE code, we derive highXH2Oof ~(0.1–1.3) × 10−5,Vtof 14–23 km s−1, andTdof 15–45 K for the CND, and the lowerXH2Oof 4 × 10−8andVtof 9 km s−1for the 20 km s−1cloud. Collisional excitation and dust effects are responsible for the water excitation in the southwest lobe of the CND and the 20 km s−1cloud, whereas only collisions can account for the water excitation in the northeast lobe of the CND. We propose that the water vapor in the CND is produced by grain sputtering by shocks of 10–20 km s−1, with some contribution of high temperature and cosmic-ray chemistries plus a photon-dominated region chemistry, whereas the lowXH2Oderived for the 20 km s−1cloud could be partially a consequence of the water freeze-out on grains.
