Galactic Fly-Bys: New Source of Lithium Production

TL;DR

This paper explores a new post-Big Bang nucleosynthesis lithium production mechanism involving cosmic rays from galaxy interactions, which could explain observed lithium abundances in low-metallicity systems like the SMC.

Contribution

It introduces a novel lithium production channel from galaxy-galaxy interaction cosmic rays, expanding understanding of lithium origins beyond standard models.

Findings

Potential significance of galaxy interaction cosmic rays in lithium production.

Implications for resolving the lithium abundance discrepancy in low-metallicity stars.

Highlights the need to consider non-standard lithium sources in cosmological models.

Abstract

Observations of low-metallicity halo stars have revealed a puzzling result: the abundance of \li7 in these stars is at least three times lower than their predicted primordial abundance. It is unclear whether the cause of this disagreement is a lack of understanding of lithium destruction mechanisms in stars or the non-standard physics behind the Big Bang Nucleosynthesis (BBN). Uncertainties related to the destruction of lithium in stars can be circumvented if lithium abundance is measured in the "pristine" gas of the low metallicity systems. The first measurement in one such system, the Small Magellanic Cloud (SMC), was found to be at the level of the pure expected primordial value, but is on the other hand, just barely consistent with the expected galactic abundance for the system at the SMC metallicity, where important lithium quantity was also produced in interactions of galactic cosmic rays (GCRs) and presents an addition to the already present primordial abundance. Due to the importance of the SMC lithium measurement for the resolution of the lithium problem, we here draw attention to the possibility of another post-BBN production channel of lithium, which could present an important addition to the observed SMC lithium abundance. Besides standard galactic cosmic rays, additional post-BBN production of lithium might come from cosmic rays accelerated in galaxy-galaxy interactions. This might be important for a system such is the SMC, which has experienced galaxy harassment in its history...(abridged)