Detecting ultralight axions from multifrequency observations of neutral hydrogen intensity mapping

TL;DR

This paper explores how ultralight axions influence neutral hydrogen intensity mapping signals, revealing potential observational signatures and degeneracies with dark energy and neutrinos in future surveys.

Contribution

It introduces a novel analysis of ULA effects on hydrogen brightness temperature fluctuations and their degeneracies with dark energy and neutrinos.

Findings

ULAs cause distinctive suppression features in angular correlations.

Degeneracies exist between ULA parameters, dark energy, and neutrino masses.

Future surveys can potentially distinguish ULA effects from other cosmological components.

Abstract

We investigate the effects of ultralight axions (ULAs) on the differential brightness temperature fluctuations of neutral hydrogen at the post-reionization stage. Unique structure suppression features under the influence of ULAs are studied from angular correlations of the neutral hydrogen signals observed at different frequencies. Moreover, ULAs can behave like dark energy or dark matter at different mass regimes, implying that the fraction of the ULA energy density would be correlated with the sum of neutrino masses and the parameters of the dark energy equation of state for dark matter and dark energy like ULAs, respectively. We have explored the parameter space for the ULA physics and possible degeneracies among dark energy, neutrinos, and ULAs using the theoretical angular correlation functions expected from future intensity mapping surveys.