Universität zu Köln

Panessa, Marco (2023). A Novel Technique for Modeling Non-Equilibrium Astrochemistry in Molecular Cloud Simulations. PhD thesis, Universität zu Köln.

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Abstract

The interstellar medium (ISM) contains numerous chemical species whose distribution can give clues to how the ISM will evolve in time. However, modeling these species self-consistently in 3D-MHD simulations is computationally expensive, so simulations are generally restricted to species whose presence affects the thermal balance of the gas. This approach is cost-effective, but sacrifices the possibility of learning more about the ISM from the excluded species. This thesis presents a novel approach to post-processing the chemistry of 3D-MHD molecular cloud simulations. The approach uses the microphysics package KROME to post-process the chemical histories of massless tracer particles in four well-resolved 3D-MHD SILCC-Zoom simulations. After post-processing, the tracer data is used to reconstruct volume-filling density grids of species which have never been modeled in a self-consistent, time-dependent manner to date, due to their computational overhead. The modeling pipeline is applied in two papers to the molecular gas tracers HCO+ and OH, the emission of which is associated with CO-bright and CO-dark molecular gas respectively. Unprecedented column density maps of these species at a spatial resolution of 0.125 pc are presented and shown to agree with observations. The time-dependent nature of the post-processing algorithm permits the analysis of the formation of HCO+ and OH, in particular their peak abundance regimes and growth timescales. In conjunction with column density maps of H2, the extinction-dependent relationship between the densities of OH and H2 can be mathematically fit from a 3D-MHD simulation for the first time. Finally, the potential application of this method to measuring the age of molecular clouds via studies of the deuterium fractionation in the gas is explored.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Panessa, Marco panessa@ph1.uni-koeln.de UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-700677
Date:	13 February 2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language "interstellar medium", "astrochemistry", "astrophysics", "simulations", "post-processing", "star formation", "molecular clouds" English
Date of oral exam:	3 May 2023
Referee:	Name Academic Title Seifried, Daniel Dr. Schilke, Peter Prof. Dr. Muecher, Dennis Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/70067