Constraint on the early-formed dark matter halos using the free-free emission in the Planck foreground analysis

Abstract

We provide a new constraint on the small-scale density fluctuations, evaluating the diffuse background free-free emission from dark matter halos in the dark ages. If there exists a large amplitude of the matter density fluctuations on small scales, the excess enhances the early formation of dark matter halos. When the virial temperature is sufficiently high, the gas in a halo is heated up and ionized by thermal collision. The heated ionized gas emits photons by the free-free process. We would observe the sum of these photons as the diffuse background free-free emission. Assuming the analytical dark matter halo model including the gas density and temperature profile, we calculate the intensity of the diffuse background free-free emission from early-formed dark matter halos in the microwave frequency range. Comparing with the recent foreground analysis on cosmic microwave background, we obtain the constraint on the excess of the density fluctuations on small scales. Our constraint corresponds to $P_{\zeta }\lesssim 10^{-7}$ for $k\simeq 1-100{\mathrm{Mpc}}^{-1}$ with assuming the delta-function-type curvature power spectrum. Therefore, our constraint is the most stringent constraint on the perturbations below $1\mathrm{Mpc}$ scales.

12 pages, 6 figures

References in corpus (7)

• Dark Energy Survey Year 3 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing
• Minimally Parametric Power Spectrum Reconstruction from the Lyman-alpha Forest
• Energy Transfer in Multi Field Inflation and Cosmological Perturbations
• Gamma-rays from ultracompact minihalos: potential constraints on the primordial curvature perturbation
• Reconstruction of the Primordial Power Spectrum using Temperature and Polarisation Data from Multiple Experiments
• Probing small-scale cosmological fluctuations with the 21 cm forest: effects of neutrino mass, running spectral index and warm dark matter
• Global radiation signature from early structure formation

Cited by in corpus (7)

• Observing nulling of primordial correlations via the 21 cm signal
• Constraining the primordial curvature perturbation using dark matter substructure
• Minihalos as probes of the inflationary spectrum: accurate boost factor calculation and new CMB constraints
• Cosmological contribution from population III stars in ultracompact minihalos
• Updated constraints on the primordial power spectrum at sub-Mpc scales
• CMB lensing from early-formed dark matter halos
• Cosmological free-free emission from dark matter halos in the $\Lambda$CDM model