Testing extreme-axion wave dark matter using the BOSS Lyman-Alpha forest data

TL;DR

This study compares different wave dark matter models using Lyman-alpha forest data, finding that some extreme-axion models fit the data better than conventional cold dark matter, potentially resolving previous tensions in dark matter mass constraints.

Contribution

It introduces and tests extreme-axion wave dark matter models against observational data, showing improved agreement over traditional models.

Findings

Some EAψDM models fit BOSS data better than CDM.

The tension in boson mass constraints is alleviated by EAψDM.

EAψDM models have unique spectral features in the matter power spectrum.

Abstract

Using cosmological particle hydrodynamical simulations and uniform ultraviolet backgrounds, we compare Lyman-$\alpha$ forest flux spectra predicted by the conventional cold dark matter (CDM) model, the free-particle wave dark matter (FP$\psi$DM) model and extreme-axion wave dark matter (EA$\psi$DM) models of different initial axion field angles against the BOSS Lyman-$\alpha$ forest absorption spectra with a fixed boson mass $m_b\sim 10^{-22}$eV. We recover results reported previously (Ir\v{s}i\v{c} et al. 2017b; Armengaud et al. 2017) that the CDM model agrees better with the BOSS data than the FP$\psi$DM model by a large margin, and we find the difference of total $\chi^2$'s is $120$ for $420$ data bins. These previous results demand a larger boson mass by a factor $>10$ to be consistent with the date and are in tension with the favoured value determined from local satellite galaxies. We however find that such tension is removed as some EA$\psi$DM models predict Lyman-$\alpha$ flux spectra agreeing better with the BOSS data than the CDM model, and the difference of total $\chi^2$'s can be as large as $24$ for the same bin number. This finding arises with no surprise since EA$\psi$DM models have unique spectral shapes with spectral bumps in excess of the CDM power near the small-scale cutoff typical of $\psi$DM linear matter power spectra as well as more extended cutoffs than FP$\psi$DM (Zhang & Chiueh 2017a,b).