Dark acoustic oscillations: Imprints on the matter power spectrum and the halo mass function

TL;DR

This paper studies how dark acoustic oscillations, caused by dark matter interactions, imprint on the matter power spectrum and halo mass function, and assesses their detectability in various cosmological observations.

Contribution

It demonstrates that dark acoustic oscillations are smoothed out in the power spectrum but remain visible in the halo mass function, providing new insights into their observational signatures.

Findings

Oscillations are smoothed in the power spectrum at low redshift.

Oscillations persist in the halo mass function until today.

Detecting these oscillations in observations is challenging due to their low amplitude.

Abstract

Many non-minimal dark matter scenarios lead to oscillatory features in the matter power spectrum induced by interactions either within the dark sector or with particles from the standard model. Observing such dark acoustic oscillations would therefore be a major step towards understanding dark matter. We investigate what happens to oscillatory features during the process of nonlinear structure formation. We show that at the level of the power spectrum, oscillations are smoothed out by nonlinear mode coupling, gradually disappearing towards lower redshifts. In the halo mass function, however, the same oscillations remain visible until the present epoch. As a consequence, dark acoustic oscillations could be detectable in observations that are either based on the halo mass function or on the high-redshift power spectrum. We investigate the effect of such oscillations on different observables, namely, the cluster mass function, the stellar-to-halo mass relation, and the Lyman-$\alpha$ flux power spectrum. We find that dark acoustic oscillations remain visible in all of these observables, but they are very extended and of low amplitude, making it challenging to detect them as distinct features in the data.