Influence of Ambient Conditions and Dust Parameters on the Thermal Desorption Rate of Ice Mantle

Abstract

In this paper, the calculations of dust temperature and thermal desorption rates in cold molecular clouds with taking into account stochastic heating of dust by an ultraviolet (UV) radiation field and cosmic rays (CRs) including secondary electrons, have been presented. The calculations for dust particles with a core radius in the range from 0.005 to 0.25 μm have been carried out. Grains with silicate and graphite cores covered by ice mantle (H₂O) with a thickness corresponding to the volume proportions between the core and mantle Sil/Gra : H₂O = 3 : 1 and 1 : 1 have been considered. For each dust composition, the most appropriate physical properties (heat capacity, absorption cross sections, and stopping power) have been used. Thermal desorption rates vary up to several orders depending on the dust size and up to a factor of two depending on the position in a cloud and dust core material. The obtained thermal desorption rates differ from the estimates available in the literature up to two orders depending on dust size and ambient conditions.