A Theoretical Approach To The Complex Chemical Evolution Of Phosphorus In The Interstellar Medium

By Keith Cowing
Status Report
September 18, 2023
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A Theoretical Approach To The Complex Chemical Evolution Of Phosphorus In The Interstellar Medium
Dependence of the formation of PO, PN and their ratio with the reaction rate coefficients ki of the 14 chemical reactions of the system. We plot the Pearson correlation r of the abundance of PO (blue bars), PN (red bars) and their ratio (green bars) with all 14 reaction rate coefficients for (a) T=10 K (b) T=100 K and (c) T=300 K, considering times t = 103 (light colors), t = 104 (vivid colors) and t = 105 yrs (dark colors). Correlations |r| > 0.05 are supported by p-values < 0.01. The correlations were calculated with sets consisting of all the combinations of 3 values of each of the 14 ki (bars), and also for a finer grid composed of 11 values of each of the 5 most influential ki (black diamonds). In all cases ki ranges from ki/10 to 10ki, being the values logarithmically distributed, and P-hydrogenation fraction fP = 0.5. -- astro-ph.SR

The study of phosphorus chemistry in the interstellar medium has become a topic of growing interest in astrobiology, because it is plausible that a wide range of P-bearing molecules were introduced in the early Earth by the impact of asteroids and comets on its surface, enriching prebiotic chemistry.

Thanks to extensive searches in recent years, it has become clear that P mainly appears in the form of PO and PN in molecular clouds and star-forming regions. Interestingly, PO is systematically more abundant than PN by factors typically of ∼1.4−3, independently of the physical properties of the observed source. In order to unveil the formation routes of PO and PN, in this work we introduce a mathematical model for the time evolution of the chemistry of P in an interstellar molecular cloud and analyze its associated chemical network as a complex dynamical system.

By making reasonable assumptions, we reduce the network to obtain explicit mathematical expressions that describe the abundance evolution of P-bearing species and study the dependences of the abundance of PO and PN on the system’s kinetic parameters with much faster computation times than available numerical methods. As a result, our model reveals that the formation of PO and PN is governed by just a few critical reactions, and fully explains the relationship between PO and PN abundances throughout the evolution of molecular clouds. Finally, the application of Bayesian methods constrains the real values of the most influential reaction rate coefficients making use of available observational data.

Marina Fernaández-Ruz, Izaskun Jimeénez-Serra, Jacobo Aguirre

Comments: To be published in Astrophysical Journal, 2023. Main text: 16 pages, Appendices: 9 pages, total length: 26 pages; 6 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR); Adaptation and Self-Organizing Systems (nlin.AO); Chemical Physics (physics.chem-ph); Computational Physics (physics.comp-ph)
Cite as: arXiv:2309.08293 [astro-ph.GA] (or arXiv:2309.08293v1 [astro-ph.GA] for this version)
Submission history
From: Jacobo Aguirre
[v1] Fri, 15 Sep 2023 10:16:26 UTC (2,419 KB)
Astrobiology, astrochemistry

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