Ultralight DM bosons with an Axion-like potential: scale-dependent constraints revisited

TL;DR

This paper investigates the cosmological effects of an axion-like scalar field as Dark Matter, revealing scale-dependent differences from standard Cold Dark Matter and Fuzzy Dark Matter, and constrains its parameters using observational data.

Contribution

It provides the first detailed study of scale-dependent physical quantities for axion-like potential Dark Matter and revisits the halo mass function considering non-linearity effects.

Findings

Enhanced power spectrum at large wave numbers due to non-linearity.

Distinct evolution of growth factors at high redshift depending on model.

Constraints on axion mass and decay parameter from Planck and Lyman-alpha data.

Abstract

A scalar field $\phi$ endowed with a trigonometric potential has been proposed to play the role of Dark Matter. A deep study of the cosmological evolution of linear perturbations, and its comparison to the Cold Dark Matter (CDM) and Fuzzy Dark Matter (FDM) cases (scalar field with quadratic potential), reveals an enhancement in the amplitude of the mass power spectrum for large wave numbers due to the non-linearity of the axion-like potential. For the first time, we study the scale-dependence on physical quantities such as the growth factor $D_k$, the velocity growth factor $f_k$, and $f_k \sigma_8$. We found that for $z<10$, all these quantities recover the CDM evolution, whereas for high redshift there is a clear distinction between each model (FDM case, and axion-like potential) depending on the wavenumber $k$ and on the decay parameter of the axion-like potential as well. A semi-analytical Halo Mass Function is also revisited, finding a suppression of the number of low mass halos, as in the FDM case, but with a small increment in the amplitude of the variance and halo mass function due to the non-linearity of the axion-like potential. Finally, we present constraints on the axion mass and the axion decay parameter by using data of the Planck Collaboration 2018 and Lyman-$\alpha$ forest.