Large-scale BAO signatures of the smallest galaxies

TL;DR

This paper explores how large-scale baryon acoustic oscillations (BAO) signatures from the smallest galaxies at high redshift can reveal early universe physics, with potential detectability using current radio telescopes.

Contribution

It demonstrates that the relative velocity between dark matter and baryons at high redshift creates amplified BAO features, offering a new observational probe of early structure formation.

Findings

Enhanced BAO oscillations at z=20 are orders of magnitude larger than previously expected.

Potential detectability of these BAO signatures with Arecibo and FAST telescopes.

The effect can inform on small-scale physics and impact dark energy measurements.

Abstract

Recent work has shown that at high redshift, the relative velocity between dark matter and baryonic gas is typically supersonic. This relative velocity suppresses the formation of the earliest baryonic structures like minihalos, and the suppression is modulated on large scales. This effect imprints a characteristic shape in the clustering power spectrum of the earliest structures, with significant power on 100 Mpc scales featuring highly pronounced baryon acoustic oscillations. The amplitude of these oscillations is orders of magnitude larger at z=20 than previously expected. This characteristic signature can allow us to distinguish the effects of minihalos on intergalactic gas at times preceding and during reionization. We illustrate this effect with the example of 21 cm emission and absorption from redshifts during and before reionization. This effect can potentially allow us to probe physics on kpc scales using observations on 100 Mpc scales. We present sensitivity forecasts for FAST and Arecibo. Depending on parameters, this enhanced structure may be detectable by Arecibo at redshifts near z=15-20, and with appropriate instrumentation FAST could measure the BAO power spectrum with high precision. In principle, this effect could also pose a serious challenge for efforts to constrain dark energy using observations of the BAO feature at low redshift.