Chia-Jung Hsu(Chalmers University of Technology); Jonathan Tan(Chalmers University of Technology); Matthew D. Goodson(University of North Carolina at Chapel Hill); Paola Caselli(Max-Planck-Institute for Extraterrestrial Physics); Bastian Körtgen(Universität Hamburg); Yu Cheng(University of Virginia)
High deuterium fraction of N2H+ (Dfrac_N2H+) is often observed in pre-stellar cores. However, the proper physical and chemical conditions to reach such high values are still under debate. To understand the required chemical conditions, we carry out a series of three-dimensional magnetohydrodynamics simulations of a massive prestellar core coupled with a sophisticated deuteration astrochemical network. We investigate the effects of initial ortho-para ratio of H2, temperature, cosmic ray ionization rate, CO depletion factor and initial chemical age. We find that high cosmic ray ionization rates and high CO depletion can allow the simulated Dfrac_N2H+ to match observational values in one free-fall time. However, while a lower initial ortho-para-ratio of H2 (OPR_H2) helps the growth of Dfrac_H2H+, the spatial structure of deuterium fraction is too widespread compared to observational data. We discuss the implications of our results for massive star formation theories.