# Hadronic Interactions of Energetic Charged Particles in Protogalactic Outflow Environments and Implications for the Early Evolution of Galaxies

## TL;DR

This paper models how energetic hadronic particles in protogalactic outflows heat the surrounding medium through pion production, affecting galaxy evolution and star formation, with implications for high-redshift galaxy observations.

## Contribution

It introduces a detailed analysis of cosmic ray heating in protogalactic outflows, comparing advection and diffusion regimes and applying the model to high-redshift galaxy data.

## Key findings

- Peak heating rate of 10^{-26} erg cm^{-3} s^{-1} at the outflow base in diffusion regime
- Heating extends up to tens of kpc in advection regime
- Approximately 10% of cosmic rays escape via advection

## Abstract

We investigate the interactions of energetic hadronic particles with the media in outflows from star-forming protogalaxies. These particles undergo pion-producing interactions which can drive a heating effect in the outflow, while those advected by the outflow also transport energy beyond the galaxy, heating the circumgalactic medium. We investigate how this process evolves over the length of the outflow and calculate the corresponding heating rates in advection-dominated and diffusion-dominated cosmic ray transport regimes. In a purely diffusive transport scenario, we find the peak heating rate reaches $10^{-26}\;\! {\rm erg~cm}^{-3}\;\! {\rm s}^{-1}$ at the base of the outflow where the wind is driven by core-collapse supernovae at an event rate of 0.1 $\text{yr}^{-1}$, but does not extend beyond 2 kpc. In the advection limit, the peak heating rate is reduced to $10^{-28}\;\! {\rm erg~cm}^{-3}\;\! {\rm s}^{-1}$, but its extent can reach to tens of kpc. Around 10% of the cosmic rays injected into the system can escape by advection with the outflow wind, while the remaining cosmic rays deliver an important interstellar heating effect. We apply our cosmic ray heating model to the recent observation of the high-redshift galaxy MACS1149-JD1 and show that it could account for the quenching of a previous starburst inferred from spectroscopic observations. Re-ignition of later star-formation may be caused by the presence of filamentary circumgalactic inflows which are reinstated after cosmic ray heating has subsided.