Observational Signatures of the First Galaxies

TL;DR

This paper reviews the potential observational signatures of Population III star clusters in the earliest galaxies, using simulations to predict their detectability with upcoming telescopes like JWST.

Contribution

It presents cosmological radiation hydrodynamics simulations of Pop III starbursts at z ~ 12, predicting their recombination line signatures and assessing their detectability.

Findings

Pop III star clusters at z > 10 are likely undetectable with next-gen telescopes.

Pop III clusters at z < 6 may be observable in deep JWST surveys.

Simulations provide time-dependent luminosities and equivalent widths of recombination lines.

Abstract

Detection of the radiation emitted from some of the earliest galaxies will be made possible in the next decade, with the launch of the James Webb Space Telescope (JWST). A significant fraction of these galaxies may host Population (Pop) III star clusters. The detection of the recombination radiation emitted by such clusters would provide an important new constraint on the initial mass function (IMF) of primordial stars. Here I review the expected recombination line signature of Pop III stars, and present the results of cosmological radiation hydrodynamics simulations of the initial stages of Pop III starbursts in a first galaxy at z ~ 12, from which the time-dependent luminosities and equivalent widths of IMF-sensitive recombination lines are calculated. While it may be unfeasible to detect the emission from Pop III star clusters in the first galaxies at z > 10, even with next generation telescopes, Pop III star clusters which form at lower redshifts (i.e. at z < 6) may be detectable in deep surveys by the JWST.