Exploration of the high-redshift universe enabled by THESEUS

TL;DR

The THESEUS mission aims to detect high-redshift gamma-ray bursts to study early universe phenomena, including galaxy formation, re-ionization, and cosmic chemical enrichment, leveraging their brightness as cosmic probes.

Contribution

This paper proposes the THESEUS mission as a novel platform for detecting and studying gamma-ray bursts at redshifts above 6, enabling transformative insights into early universe processes.

Findings

Anticipated detection of large samples of high-z GRBs.

Potential to constrain re-ionization history beyond z>6.

Ability to study early chemical enrichment and Population III stars.

Abstract

At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer of star formation and star-forming galaxies over the whole of cosmic history. Their bright power-law afterglows provide ideal backlights for absorption studies of the interstellar and intergalactic medium back to the reionization era. The proposed THESEUS mission is designed to detect large samples of GRBs at $z>6$ in the 2030s, at a time when supporting observations with major next generation facilities will be possible, thus enabling a range of transformative science. THESEUS will allow us to explore the faint end of the luminosity function of galaxies and the star formation rate density to high redshifts; constrain the progress of re-ionisation beyond $z\gtrsim6$; study in detail early chemical enrichment from stellar explosions, including signatures of Population III stars; and potentially characterize the dark energy equation of state at the highest redshifts.