Spoon or slide? The non-linear matter power spectrum in the presence of massive neutrinos

TL;DR

This paper explains the origin of the spoon-shaped feature in the non-linear matter power spectrum caused by massive neutrinos, using the halo model to accurately predict its characteristics and evolution.

Contribution

The study demonstrates that the spoon feature arises from the transition between two-halo and one-halo power spectra and shows that the halo model can reliably predict this feature without parameter tuning.

Findings

The spoon feature results from the transition in the halo model.

Halo model predictions match simulations for the spoon's properties.

Non-linear perturbative inputs improve high-redshift predictions.

Abstract

Numerical simulations of massive neutrino cosmologies consistently find a spoon-like feature in the non-linear matter power spectrum ratios of cosmological models that differ only in the neutrino mass fraction f_N. Typically, the ratio approaches unity at low wave numbers k, decreases by ~ 10 f_N at k ~ 1 h/Mpc, and turns up again at large k. Using the halo model of large-scale structure, we show that this spoon feature originates in the transition from the two-halo power spectrum to the one-halo power spectrum. The former's sensitivity to f_N rises with k, while that of the latter decreases with k. The presence of this spoon feature is robust with respect to different choices of the halo mass function and the halo density profile, and does not require any parameter tuning within the halo model. We demonstrate that a standard halo model calculation is already able to predict the depth, width, and position of this spoon as well as its evolution with redshift z with remarkable accuracy. Predictions at z >= 1 can be further improved using non-linear perturbative inputs.