New Roads to the Small-Scale Universe: Measurements of the Clustering of Matter with the High-Redshift UV Galaxy Luminosity Function

TL;DR

This paper uses high-redshift UV galaxy luminosity data to measure the small-scale matter power spectrum, providing new insights into dark matter clustering during cosmic dawn and reionisation.

Contribution

It presents the first measurements of the matter power spectrum at small scales and high redshifts using UV galaxy luminosity functions, extending the observational regime.

Findings

Measured the matter power spectrum at 0.5-10 Mpc^{-1} with ~30% precision.

Covered redshift range 4 to 10, beyond previous large-scale observations.

Demonstrated UV luminosity functions as a new tool for probing dark matter properties.

Abstract

The epochs of cosmic dawn and reionisation present promising avenues for understanding the role of dark matter (DM) in our cosmos. The first galaxies that populated the Universe during these eras resided in DM halos that were much less massive than their counterparts today. Consequently, observations of such galaxies can provide us with a handle on the clustering of DM in an otherwise currently inaccessible regime. In this work, we use high-redshift UV galaxy luminosity-function (UV LF) data from the Hubble Space Telescope to study the clustering properties of DM at small scales. In particular, we present new measurements of the matter power spectrum at wavenumbers $0.5\,\mathrm{Mpc}^{-1} < k < 10\,\mathrm{Mpc}^{-1}$ to roughly 30% precision, obtained after marginalising over the unknown astrophysics. These new data points cover the uncharted redshift range $4\leq z\leq 10$ and encompass scales beyond those probed by Cosmic-Microwave-Background and large-scale-structure observations. This work establishes the UV LF as a powerful tool to probe the nature of DM in a different regime than other cosmological and astrophysical data sets.