ORIGINAL RESEARCH article

Front. Astron. Space Sci.

Sec. Astrochemistry

Volume 12 - 2025 | doi: 10.3389/fspas.2025.1570525

This article is part of the Research TopicPhosphorus Chemistry in the Interstellar Medium and Planetary AtmospheresView all 5 articles

Strong parameter hierarchy in the interstellar phosphorus chemical network

Provisionally accepted
  • 1Center for Astrobiology, Spanish National Research Council (CSIC), Madrid, Spain
  • 2Comillas Pontifical University, Madrid, Madrid, Spain

The final, formatted version of the article will be published soon.

Phosphorus-bearing molecules are fundamental for life on Earth, yet their astrochemical origins remain poorly understood. Their formation in the interstellar medium has been challenging to elucidate due to limited spectroscopic detections and the reliance on theoretical models that depend on numerous kinetic parameters whose values are very uncertain. Multi-parameter models often suffer from ``sloppiness'', where many parameter combinations exhibit negligible influence on model outcomes, while a few dominate system behavior. In this study, we introduce the Fisher Information Spectral Reduction (FISR) algorithm, a novel and computationally efficient method to reduce the complexity of such sloppy models. Our approach exposes the strong parameter hierarchy governing these systems by identifying and eliminating parameters associated with insensitive directions in the parameter space. Applying this methodology to the phosphorus astrochemistry network, \textcolor{red}{we reduce the number of reaction rate coefficients from 14 to 3, pinpointing the key reactions and kinetic parameters responsible for forming PO and PN}, the main phosphorus-bearing molecules typically detected in interstellar space. The simplified model retains its predictive accuracy, offering deeper insights into the mechanisms driving phosphorus chemistry in the interstellar medium. This methodology is applicable to multi-parameter models of any kind and, specifically in astrochemistry, facilitates the development of simpler, more realistic and interpretable models to effectively guide targeted observational efforts.

Keywords: Phosphorus Astrochemistry, Interstellar Medium, Astrobiology, dynamical systems, chemical reaction networks, Kinetic parameters, Complexity reduction, Parameter sensitivity

Received: 03 Feb 2025; Accepted: 10 Jul 2025.

Copyright: © 2025 Fernández-Ruz, Jimenez-Serra, Castro, Ruiz-Bermejo and Aguirre. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Jacobo Aguirre, Center for Astrobiology, Spanish National Research Council (CSIC), Madrid, Spain

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