The first detections of the key prebiotic molecule PO in star-forming regions

TL;DR

This study reports the first detection of the prebiotic molecule PO in star-forming regions, revealing its formation pathways and abundance, which are crucial for understanding phosphorus chemistry in early planetary systems.

Contribution

It presents the first detection of PO in star-forming regions and models its formation and abundance, advancing knowledge of prebiotic chemistry in such environments.

Findings

PO detected in W51 e1/e2 and W3(OH) regions

PO/PN abundance ratios of 1.8 and 3 respectively

Chemical model predicts observed abundances with high initial phosphorus

Abstract

Phosphorus is a crucial element in prebiotic chemistry, especially the P$-$O bond, which is key for the formation of the backbone of the deoxyribonucleic acid. So far, PO had only been detected towards the envelope of evolved stars, and never towards star-forming regions. We report the first detection of PO towards two massive star-forming regions, W51 e1/e2 and W3(OH), using data from the IRAM 30m telescope. PN has also been detected towards the two regions. The abundance ratio PO/PN is 1.8 and 3 for W51 and W3(OH), respectively. Our chemical model indicates that the two molecules are chemically related and are formed via gas-phase ion-molecule and neutral-neutral reactions during the cold collapse. The molecules freeze out onto grains at the end of the collapse and desorb during the warm-up phase once the temperature reaches $\sim$35 K. The observed molecular abundances of 10$^{-10}$ are predicted by the model if a relatively high initial abundance of phosphorus, 5$\times$10$^{-9}$, is assumed.