Class II 6.7 GHz Methanol Maser Association with Young Massive Cores Revealed by ALMA

Abstract

We explored the implication of the association (or lack of it) of 6.7 GHz class II methanol (CH 3 OH) masers with massive dense cores (MDCs) detected (within a sample of ATLASGAL selected infrared quiet massive clumps) at 0.9 mm with Atacama Large Millimeter/submillimeter array. We found 42 out of the 112 cores (37.5%) detected with the Atacama Compact Array (ACA) to be associated with 6.7 GHz CH 3 OH masers. The lowest mass core with CH 3 OH maser association is . The angular offsets of the ACA cores from the 6.7 GHz CH 3 OH maser peak positions range from 0.″17 to 4.″79, with a median value of 2.″19. We found a weak correlation between the 0.9 mm continuum (MDCs) peak fluxes and the peak fluxes of their associated methanol multibeam (MMB) 6.7 GHz CH 3 OH masers. About 90% of the cores associated with 6.7 GHz CH 3 OH masers have masses of >40 M ⊙ . The CH 3 OH maser containing cores are candidates for embedded high-mass protostellar objects in their earliest evolutionary stages. With our ACA 0.9 continuum data compared with the MMB 6.7 GHz CH 3 OH maser survey, we have constrained the cores already housing massive protostars based on their association with the radiatively pumped 6.7 GHz CH 3 OH masers.