Quark-Novae, cosmic reionization, and early r-process element production

TL;DR

This paper explores how Quark-Novae could have contributed to the universe's reionization and early heavy element production, proposing they produce enough photons to reionize hydrogen and contribute to r-process elements, with observable gamma-ray bursts at high redshifts.

Contribution

It introduces Quark-Novae as a source for reionization and early r-process elements, linking their occurrence to observable gamma-ray bursts at high redshifts.

Findings

Quark-Novae can produce sufficient photons to reionize hydrogen by z ~ 6.

They contribute to r-process element abundances for atomic numbers A > 130.

Predicted gamma-ray bursts from Quark-Novae cluster at z ~ 7-8.

Abstract

We examine the case for Quark-Novae (QNe) as possible sources for the reionization and early metal enrichment of the universe. Quark-Novae are predicted to arise from the explosive collapse (and conversion) of sufficiently massive neutron stars into quark stars. A Quark-Nova (QN) can occur over a range of time scales following the supernova event. For QNe that arise days to weeks after the supernovae, we show that dual-shock that arises as the QN ejecta encounter the supernova ejecta can produce enough photons to reionize hydrogen in most of the Inter-Galactic medium (IGM) by z ~ 6. Such events can explain the large optical depth tau_e ~ 0.1 as measured by WMAP, if the clumping factor, C, of the material being ionized is smaller than 10. We suggest a way in which a normal initial mass function (IMF) for the oldest stars can be reconciled with a large optical depth as well as the mean metallicity of the early IGM post reionization. We find that QN also make a contribution to r-process element abundances for atomic numbers A > 130. We predict that the main cosmological signatures of Quark-Novae are the gamma-ray bursts that announce their birth. These will be clustered at redshifts in the range z ~ 7-8 in our model.