Combined hydrodynamic and gas-grain chemical modeling of hot cores

I. One-dimensional simulations

¹ Department of Chemistry, University of Virginia, Charlottesville, VA 29904-4319, USA
² Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325, USA
e-mail: rgarrod@virginia.edu

Received: 21 August 2020
Accepted: 3 April 2021

Abstract

Context. Gas-grain models have long been employed to simulate hot-core chemistry; however, these simulations have traditionally neglected to couple chemical evolution in tandem with a rigorous physical evolution of a source. This over-simplification particularly lacks an accurate treatment of temperature and spatial distribution, which are needed for realistic simulations of hot cores.

Aims. We aim to combine radiation hydrodynamics (RHD) with hot-core chemical kinetics in one dimension to produce a set of astrochemical models that evolve according to explicitly calculated temperature, density, and spatial profiles.

Methods. We solve radiation hydrodynamics for three mass-accretion-rate models using Athena++. We then simulate the chemistry using the hot-core chemical kinetic code MAGICKAL according to the physics derived from the RHD treatment.

Results. We find that as the mass-accretion rate decreases, the overall gas density of the source decreases. In particular, the gas density for the lowest mass-accretion rate is low enough to restrict the proper formation of many complex organic molecules. We also compare our chemical results in the form of calculated column densities to those of observations toward Sgr B2(N2). We find a generally good agreement for oxygen-bearing species, particularly for the two highest mass-accretion rates.

Conclusions. Although we introduce hot-core chemical modeling using a self-consistent physical treatment, the adoption of a two-dimensional model may better reproduce chemistry and physics toward real sources and thus achieve better chemical comparisons with observations.