Title: Impact of Dust Grain Distribution on the Chemical Evolution in the ISM

Speaker: Dr. Wasim IQBAL (South-Western Institute For Astronomy Research at Yunnan University)

Time: 10:30am, July 15, 2021

Location: 5-516, PMO Xianlin Campus

Abstract: Many chemical reactions occur at the surface of interstellar dust grains, producing a large diversity of molecules more or less complex. Most current astrochemical models include only a single size of grains (0.1 micron representing most of the mass of silicate grains) to study the formation and destruction of molecules on the dust surface. We have studied the effect of considering a distribution of grain sizes on the chemical evolution of various complex molecules in cold clouds in the ISM.

We also show how different types of grain size distributions can impact the chemical evolution in the ISM. In our model, each grain has its own grain number density which comes from either MRN or WD distribution. Other important parameters such as grain surface temperature or cosmic ray induced desorption also vary with grain sizes. We present abundances of various molecules including some complex molecules in the gas phase and also on the surface of dust grains at different time intervals during the simulation. We also compare our results with observed abundances in TMC-1 and L134N. We show how a multi grain model can be a better tool in explaining the observed abundances in these cold dense clouds.