Hot-gas cold-dust pumping for water masers associated with H II regions

Abstract

view Abstract Citations (49) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hot-gas cold-dust pumping for water masers associated with H II regions Deguchi, S. Abstract A collisional pump with an internal sink is proposed for the water masers associated with H II regions, where the population inversion occurs due to the absorption by cold ice-mantle grains in a highly dusty cloud of the far-infrared line radiation of hot water vapor. A new escape probability method is developed to calculate the transfer of line radiation in dusty medium. The pump mechanism explains the power of usual maser sources associated with H II regions and the enormous power of the sources associated with W49 N and external galaxies. Models of maser clouds have a radius of 5 x 10 to the 15th-10 to the 16th cm, an H2 number density of 4 x 10 to the 9th/cu cm, an expansion velocity of 10-30 km/s, a kinetic temperature of 350 K, and a grain temperature of 100 K. Giant maser sources require grains of the size about 1 micron. The apparent size of the emission spots (approximately 10 to the 13th cm) observed by VLBI is interpreted as due to a fluctuation in the cloud, and the assembly of the spots is spread within a size of 10 to the 16th cm. The temperature difference between the dust and gas is due to a relaxation process after an infrared burst accompanying protostar formation. Publication: The Astrophysical Journal Pub Date: October 1981 DOI: 10.1086/159270 Bibcode: 1981ApJ...249..145D Keywords: Cosmic Dust; H Ii Regions; High Temperature Gases; Interstellar Masers; Nebulae; Water Masers; Astronomical Models; Far Infrared Radiation; Interstellar Matter; Radiative Transfer; Water Vapor; Astrophysics full text sources ADS |