The abundance of HNCO and its use as a diagnostic of environment

摘要: Aims. We aim to investigate the chemistry and gas phase abundance of HNCO variation HNCO/CS ratio as a diagnostic physics in regions massive star formation. Methods. A numerical-chemical model has been developed which self-consistently follows chemical evolution hot core. The comprises two distinct stages. first stage isothermal, modified free-fall collapse molecular dark cloud. This is immediately followed by an increase temperature represents switch on central subsequent hot, dense cloud (the core). During phase, species are allowed accrete grain surfaces where they can participate further reactions. core surface thermally desorb back ambient takes place. For comparison, network was also used simple photodissociation regions. Results. Our investigation reveals that inefficiently formed when only gas-phase formation pathways considered with reaction rates consistent existing laboratory data. particularly true at low temperatures but up ∼200 K. Using currently measured rates, obtaining observed abundances requires its – similar other “hot core” such CH3OH. However our shows cores not direct product evaporation mantles. show varies function time match range values observed. unambiguously related UV field suggested results inconsistent hypothesis Martin et al. (2008, ApJ, 678, 245). In addition, this extremely sensitive initial sulphur abundance. find grows monotonically absolute value scales approximately linearly S early times.