Cthulhu: An Open Source Molecular and Atomic Cross Section Computation Code for Substellar Atmospheres

Atmospheric studies of exoplanets and brown dwarfs are a cutting-edge and rapidly evolving area of astrophysics research. Calculating models of exoplanet or brown dwarf spectra requires knowledge of the wavelength-dependent absorption of light (cross sections) by the molecules and atoms in the atmosphere.

Here we introduce Cthulhu, a pure Python package that rapidly calculates cross sections from atomic and molecular line lists.

Cthulhu includes modules to automatically download molecular line lists from online databases (e.g. ExoMol and HITRAN) and compute cross sections on a user-specified temperature, pressure, and wavenumber grid. Cthulhu requires only CPUs and can run on a user’s laptop (for smaller line lists with < 100 million lines) or on a large cluster in parallel (for many billion lines).

Cthulhu includes in-depth Jupyter tutorials in the online documentation. Finally, Cthulhu can be used as an educational tool to demystify the process of making cross sections for atmospheric models.

The role and applications of the Cthulhu Python package. Cthulhu can download molecular and atomic line lists and calculate the corresponding absorption cross sections as a function of temperature, pressure, and wavenumber. Cross sections made by Cthulhu can be used in radiative transfer codes to calculate model spectra of exoplanet and brown dwarf atmospheres. — astro-ph.IM

Arnav Agrawal, Ryan J. MacDonald

Comments: 7 pages, 1 figure, published in JOSS. Summon Cthulhu at this https URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2410.14751 [astro-ph.IM] (or arXiv:2410.14751v1 [astro-ph.IM] for this version)
https://doi.org/10.48550/arXiv.2410.14751
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Journal reference: Journal of Open Source Software (2024): 9(102), 6894
Related DOI:
https://doi.org/10.21105/joss.06894
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Submission history
From: Ryan MacDonald
[v1] Thu, 17 Oct 2024 23:35:21 UTC (7,352 KB)
https://arxiv.org/abs/2410.14751

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