The Chemical Evolution of Phosphorus

TL;DR

This study measures phosphorus abundances in stars across a range of metallicities using Hubble spectra, revealing insights into its nucleosynthetic origins and the role of hypernovae in early chemical evolution.

Contribution

First measurement of phosphorus in low-metallicity stars using UV spectra, providing new data to refine chemical evolution models of phosphorus.

Findings

Massive-star P yields may need to be increased in models.

Hypernovae significantly contributed to early phosphorus production.

Phosphorus abundance trends support the role of hypernovae in early universe.

Abstract

Phosphorus is one of the few remaining light elements for which little is known about its nucleosynthetic origin and chemical evolution, given the lack of optical absorption lines in the spectra of long-lived FGK-type stars. We have identified a P I doublet in the near-ultraviolet (2135/2136 A) that is measurable in stars of low metallicity. Using archival Hubble Space Telescope-STIS spectra, we have measured P abundances in 13 stars spanning -3.3 <= [Fe/H] <= -0.2, and obtained an upper limit for a star with [Fe/H] ~ -3.8. Combined with the only other sample of P abundances in solar-type stars in the literature, which spans a range of -1 <= [Fe/H] <= +0.2, we compare the stellar data to chemical evolution models. Our results support previous indications that massive-star P yields may need to be increased by a factor of a few to match stellar data at all metallicities. Our results also show that hypernovae were important contributors to the P production in the early universe. As P is one of the key building blocks of life, we also discuss the chemical evolution of the important elements to life, C-N-O-P-S, together.