Kindling the First Stars II: Dependence of the Predicted PISN Rate on the Pop III Initial Mass Function

TL;DR

This paper investigates how the predicted rates of pair instability supernovae (PISN) from Population III stars depend on the initial mass function (IMF), aiming to use PISN observations to constrain the properties of the first stars.

Contribution

It models the dependence of high-redshift PISN rates on different Pop III IMFs and the method of IMF population, informing future observational constraints.

Findings

Predicted PISN rates at z>15 range from 10^-2 to 10^2 per deg^2 per year.

Estimated detection rates for JWST and Roman vary widely depending on IMF assumptions.

Modeling PISN rates is essential for using upcoming observations to constrain the Pop III IMF.

Abstract

Population III (Pop III) stars formed out of metal free gas in minihalos at $z>20$. While their ignition ended the Dark Ages and begin enrichment of the IGM, their mass distribution remains unconstrained. To date, no confirmed Pop III star has been observed and their direct detection is beyond the reach of the James Webb Space Telescope (JWST) without gravitational lensing. However, a subset of massive Pop III stars end their lives in pair instability supernova (PISN). With typical energies of $\sim10^{53}$~erg, PISN light curve peaks are bright enough to be detectable by JWST and the Roman Space Telescope. The fundamental question of this work is whether or not observed PISN can be used as a diagnostic of the Pop III IMF. In this work, we use a model of the formation of the first stars to determine the dependence of PISN rates at $z~>~5$ for a range of Pop III power law IMFs ($\alpha~=~0.2~-~2.35$) and, critically, the method by which the IMF is populated. At $z~>~15$, we predict typical rates of $10^{-2}~-~10^2$ per deg$^{2}$ per year which will produce $10^{-3}~-~0.1$/year in a single NIRCam pointing and $0.003~-~30$/year in a single Roman pointing with $0.1~-~1000$ per year detected in the HLTDS. Our work highlights that theoretical modeling of PISN rates is required if upcoming PISN studies with JWST and Roman are going to constrain the Pop III IMF.