Modelling the chemistry of star forming filaments - H$_2$ and CO chemistry

TL;DR

This paper presents advanced 3D-MHD simulations of star forming filaments incorporating a large chemical network to study H$_2$ and CO chemistry, revealing detailed chemical and thermal structures consistent with observations.

Contribution

It introduces the first implementation of a large chemical network with 37 species in 3D-MHD simulations using the KROME package, enabling detailed chemical modeling of star forming filaments.

Findings

Gradual conversion of hydrogen from H to H$_2$ in filament centers.

Decrease of dust temperature towards filament centers consistent with observations.

Chemical and thermal structures depend on radiation field and cosmic ray ionization rates.

Abstract

We present simulations of star forming filaments incorporating on of the largest chemical network used to date on-the-fly in a 3D-MHD simulation. The network contains 37 chemical species and about 300 selected reaction rates. For this we use the newly developed package KROME (Grassi et al. 2014). We combine the KROME package with an algorithm which allows us to calculate the column density and attenuation of the interstellar radiation field necessary to properly model heating and ionisation rates. Our results demonstrate the feasibility of using such a complex chemical network in 3D-MHD simulations on modern supercomputers. We perform simulations with different strengths of the interstellar radiation field and the cosmic ray ionisation rate. We find that towards the centre of the filaments there is gradual conversion of hydrogen from H to H$_2$ as well as of C$^+$ over C to CO. Moreover, we find a decrease of the dust temperature towards the centre of the filaments in agreement with recent HERSCHEL observations.