Collisional Pumping of H2O and CH3OH Masers in C-Type Shock Waves

The collisional pumping of H2O and CH3OH masers in magnetohydrodynamic nondissociative C-type shocks is considered. A grid of C-type shock models with speeds in the range 5-70 km s(-1) and preshock gas densities n(H2),(0) = 104-107 cm(-3) is constructed. The large velocity gradient approximation is used to solve the radiative transfer equation in molecular lines. The para-H2O 183.3 GHz and ortho-H2O 380.1 and 448.0 GHz transitions are shown to be inverted and to have an optical depth along the shock velocity vertical bar tau vertical bar similar to 1 at relatively low gas densities in the maser zone, n(H2) greater than or similar to 105-106 cm(-3). Higher gas densities, nH(2 )greater than or similar to 107 cm(-3), are needed for efficient pumping of the remaining H2O masers. Simultaneous generation of H2O and class I CH3OH maser emission in a shock is possible at preshock gas densities n(H2),(0) approximate to 105 cm(-3) and shock speeds in the range us approximate to 17.5-22.5 km s(-1). The possibility of detecting class I CH3OH and para-H2O 183.3 GHz masers in star-forming regions and near supernova remnants is investigated.