Effect of ULAs on the matter power spectrum recovered assuming the Planck Collaboration VI (2020) cosmological values (Ω_Λ ≈ 0.7, Ω_m + Ω_a ≈ 0.3) at z = 0.1. On the left, the change in the matter power spectrum with varying ULA mass is shown when the relative ULA density is fixed to Ω_a/(Ω_cdm + Ω_a) = 0.5. The panel on the right displays the dependence of the power spectrum on varying ULA abundance at a fixed ULA mass of m_a = 10⁻²⁵ eV. The concordance ΛCDM model is shown in a black curve on both panels. Small-scale suppression becomes stronger with decreasing ULA mass and increasing ULA abundance. For higher ULA masses of m_a ≫ 10⁻²² eV, the matter power spectrum becomes indistinguishable from the one in a ΛCDM cosmology, as is the case for Ω_a → 0.