The signature of the first stars in atomic hydrogen at redshift 20

TL;DR

This paper presents a simulation of the first stars at redshift 20, revealing a large-scale 21-cm fluctuation signal influenced by gas heating and velocity effects, detectable with current radio arrays.

Contribution

It provides the first comprehensive simulation including gas heating and velocity effects, predicting a distinct 21-cm fluctuation signature at high redshift.

Findings

Enhanced 10 mK fluctuation signal on 100-Mpc scale

Flat power spectrum with baryon acoustic oscillations

Detectable with 1000-hour observations using current radio arrays

Abstract

Dark and baryonic matter moved at different velocities in the early Universe, which strongly suppressed star formation in some regions. This was estimated to imprint a large-scale fluctuation signal of about 2 mK in the 21-cm spectral line of atomic hydrogen associated with stars at a redshift of 20, although this estimate ignored the critical contribution of gas heating due to X-rays and major enhancements of the suppression. A large velocity difference reduces the abundance of halos and requires the first stars to form in halos of about a million solar masses, substantially greater than previously expected. Here we report a simulation of the distribution of the first stars at z=20 (cosmic age of ~180 Myr), incorporating all these ingredients within a 400 Mpc box. We find that the 21-cm signature of these stars is an enhanced (10 mK) fluctuation signal on the 100-Mpc scale, characterized by a flat power spectrum with prominent baryon acoustic oscillations. The required sensitivity to see this signal is achievable with an integration time of a thousand hours with an instrument like the Murchison Wide-field Array or the Low Frequency Array but designed to operate in the range of 50-100 MHz.