Hypernova signatures of the first stars in dwarf galaxies in the local group

Abstract

ABSTRACT Observing the first generation of stars, Population III (Pop III), is still a challenge even with the JWST due to their faintness. Instead, searching for fossil records of Pop III stars in nearby dwarf galaxies provides an alternative method for studying their physical properties. It is intriguing that a star recently discovered in the Sculptor dwarf galaxy, named AS0039, is considered to show the unique signature of a Pop III star. The detailed abundance patterns of AS0039 are well matched with those predicted by nucleosynthesis models for Pop III exploding as an energetic hypernova (HN), confirming its potential to provide insight into the properties of the first stars. This study aims to explore the environmental conditions required for the formation of such a unique star using cosmological hydrodynamic zoom-in simulations on dwarf galaxies with a mass of $M_{\rm vir}\approx 10^8{\ \mathrm{ M}_\odot }$ at z = 0 while varying the fraction of Pop III stars that undergo HNe. Our simulations identify rapid gas inflow ($\dot{M}_{\rm gas}\sim 0.08{\ \mathrm{ M}_\odot }$ $\rm yr^{-1}$) as a possible factor in facilitating the formation of stars similar to AS0039. Alternatively, the delayed formation of subsequent Population II (Pop II) stars in the gas-enriched environment may lead to low-metallicity stars like AS0039. Additionally, using the a-sloth code, we investigate the probability of finding remnants of Pop II stars with HN signatures in nearby dwarf satellite galaxies. We suggest that the most likely dwarf galaxies to contain HN signatures are massive satellites with a probability of 40 per cent in the range of $M_{\rm peak}\approx 10^{10}\ \mathrm{ to} \ 10^{11}{\ \mathrm{ M}_\odot }$ and $M_{\ast }\approx 10^7 \ \mathrm{ to} \ 10^8{\ \mathrm{ M}_\odot }$, considering observational limitations.