A sensitivity analysis of interstellar ice chemistry in astrochemical models

Tobias Dijkhuis*, Thanja Lamberts*, Serena Viti & Herma Cuppen

DOI: .........

Paper

You can find a PDF of the paper here (todo), or on arXiv here (todo).

BibTex entry

@article{Dijkhuis2025,
    title = {A sensitivity analysis of interstellar ice chemistry in astrochemical models},
    author = {Dijkhuis, Tobias M. and Lamberts, Thanja and Viti, Serena and Herma, Cuppen M.},
    year = {2025},
    doi = {},
    url = {},
    month = {},
    journal = {Astronomy \& Astrophysics}, % Replace by \aap if possible
    publisher = {EDP Sciences},
    volume = {},
    number = {},
    issue = {}
    pages = {},
}

Replicating results

All the data shown in the paper (and much more) can be generated using the scripts provided in this repository.

Environment setup

I would recommend creating a new python environment, to make sure that you have all of the required packages, and none of the packages conflict with the ones installed on your system before.

The environment that was used for calculations and data analysis can be copied and activated by doing

conda env create -f environment.yml
conda activate sensitivity_analysis_ices

Then, install UCLCHEM into this new environment

cd model
python3 -m pip install -e .

This will take some time, because UCLCHEM will be need to be compiled.

Note: This is a custom version of UCLCHEM, so you need to use the one provided in this repository.

Data generation

The data for the standard cosmic ray ionization rate ($\zeta=1.3\times10^{-17}$ $\text{s}^{-1}$) and UV field strength ($F_{\mathrm{UV}}=1$ Habing) can be obtained from the Zenodo repository. After downloading this data and putting it in the 02_data directory and extracting the contents you should be good to go. The contents can be extracted by doing (on Ubuntu at least, check for your specific operating system)

unzip varying_all.zip 

or

unzip varying_reactions.zip

This should result in two directories, varying_all and varying_reactions. The first varies all parameters, and the second varies only the reaction energy barriers, but with a wider distribution (used for Fig. D3 in the paper).

If desired, the data for other values of the cosmic ray ionization rate and UV field strengths can be generated as such.

cd 01_data_generation
python3 run_sensitivity_analysis.py

Note: You need to specify the desired destination directory manually in run_sensitivity_analysis.py.

Data analysis

Once the data has been generated, it can be analyzed using tools in the data analysis directory. In create_figures.py, there is code to create all the figures shown in the paper.

cd 03_data_analysis
python3 create_figures.py

You can also use this code as inspiration for different analyses, like for different species.

Figures

All the created figures will be placed in the figures directory. This already contains all figures used in the paper.

Additional figures, not shown in the paper, can be created by doing

cd 03_data_analysis
python3 create_additional_figures.py

This creates a bunch of additional figures, similar to Figure 2 but for different physical conditions. They are shown in the directory 05_additional_figures.

Corresponding authors

• Tobias Dijkhuis: t.m.dijkhuis@lic.leidenuniv.nl
• Thanja Lamberts: a.l.m.lamberts@lic.leidenuniv.nl

ORCID

• Tobias Dijkhuis: https://orcid.org/0009-0009-2498-6429
• Thanja Lamberts: https://orcid.org/0000-0001-6705-2022
• Serena Viti: https://orcid.org/0000-0001-8504-8844
• Herma Cuppen: https://orcid.org/0000-0003-4397-0739