Ultralight axions and the kinetic Sunyaev-Zel'dovich effect

Measurements of secondary cosmic microwave background (CMB) anisotropies, such as the Sunyaev-Zel'dovich (SZ) effect, will enable new tests of neutrino and dark sector properties. The kinetic SZ (kSZ) effect is produced by cosmological flows, probing structure growth. Ultralight axions (ULAs) are a well-motivated dark-matter candidate. Here, the impact of ULA dark matter (with mass 10(-27) to 10(-23) eV) on kSZ observables is determined, applying new analytic expressions for pairwise cluster velocities and Ostriker-Vishniac signatures in structure-suppressing models. For the future CMB Stage 4 and ongoing Dark Energy Spectroscopic Instrument galaxy surveys, the kSZ effect (along with primary anisotropies) will probe ULA fractions eta(a) = Omega(axion)/Omega(DM) as low as similar to 5% if m(a) similar or equal to 10(-27) eV (at 95% C.L.), with sensitivity extending up to m a 10 -25 eV. If reionization and the primary CMB can be adequately modeled, Ostriker-Vishniac measurements could probe values eta(a) = 10(-3) if 10(-2)7 eV less than or similar to m(a) less than or similar to 10(-24) eV, or eta(a) similar or equal to 1 if m(a)similar or equal to 10(-22) eV, within the fuzzy dark matter window.

Automated summary

This paper investigates the impact of ultralight axion dark matter on the kinetic Sunyaev-Zel'dovich (kSZ) effect and provides new analytic expressions for calculating the observables. The results indicate that future CMB measurements have the potential to detect the presence of axion dark matter and estimate its mass range.