Probing small-scale baryon and dark matter isocurvature perturbations with cosmic microwave background anisotropies

Abstract

The Universe's initial conditions, in particular baryon and cold dark matter (CDM) isocurvature perturbations, are poorly constrained on sub-Mpc scales. In this paper, we develop a new formalism to compute the effect of small-scale baryon perturbations on the mean free-electron abundance, thus on cosmic microwave background (CMB) anisotropies. Our framework can accommodate perturbations with arbitrary time and scale dependence. We apply this formalism to four different combinations of baryon and CDM isocurvature modes, and use Planck CMB-anisotropy data to probe their initial amplitude. We find that Planck data is consistent with no small-scale isocurvature perturbations, and that this additional ingredient does not help alleviate the Hubble tension. We set upper bounds to the dimensionless initial power spectrum ${\Delta }_{\mathcal{I}}^2(k)$ of these isocurvature modes at comoving wavenumbers $1{\text{Mpc}}^{-1}\le k\le 10^3$ Mpc${}^{-1}$, for several parameterizations. For a scale-invariant power spectrum, our 95% confidence-level limits on ${\Delta }_{\mathcal{I}}^2$ are 0.023 for pure baryon isocurvature, 0.099 for pure CDM isocurvature, 0.026 for compensated baryon-CDM perturbations, and 0.009 for joint baryon-CDM isocurvature perturbations. Using a Fisher analysis generalized to non-analytic parameter dependence, we forecast that a CMB Stage-4 experiment would be able to probe small-scale isocurvature perturbations with initial power 3 to 10 times smaller than Planck limits. The formalism introduced in this work is very general and can be used more widely to probe any physical processes or initial conditions sourcing small-scale baryon perturbations.

arXiv comment17 pages, 7 figures. Results are available at https://github.com/nanoomlee/small-scale_baryon_CDM_isocurvature_results

References in corpus (63)

• Planck 2015 results. XIII. Cosmological parameters
• Planck 2018 results. X. Constraints on inflation
• The Cosmic Linear Anisotropy Solving System (CLASS) II: Approximation schemes
• Baryonic Features in the Matter Transfer Function
• Cosmological Perturbation Theory in the Synchronous vs. Conformal Newtonian Gauge
• Cosmological Perturbation Theory in the Synchronous and Conformal Newtonian Gauges
• The Cosmic Microwave Background Spectrum from the Full COBE/FIRAS Data Set
• An absorption profile centred at 78 megahertz in the sky-averaged spectrum
• Karhunen-Loeve eigenvalue problems in cosmology: how should we tackle large data sets?
• Nongaussian Isocurvature Perturbations from Inflation
• The Primordial Inflation Explorer (PIXIE): A Nulling Polarimeter for Cosmic Microwave Background Observations
• Possible interaction between baryons and dark-matter particles revealed by the first stars
• Relative velocity of dark matter and baryonic fluids and the formation of the first structures
• The evolution of CMB spectral distortions in the early Universe
• Probing the inflaton: Small-scale power spectrum constraints from measurements of the CMB energy spectrum
• PArthENoPE: Public Algorithm Evaluating the Nucleosynthesis of Primordial Elements
• HyRec: A fast and highly accurate primordial hydrogen and helium recombination code
• Metric perturbations in two-field inflation
• CMB at 2x2 order: the dissipation of primordial acoustic waves and the observable part of the associated energy release
• The General Primordial Cosmic Perturbation
• Relieving the Hubble tension with primordial magnetic fields
• Power Spectrum Constraints from Spectral Distortions in the Cosmic Microwave Background
• Isocurvature Perturbations in Multiple Inflationary Models
• Efficient Cosmological Parameter Estimation from Microwave Background Anisotropies
• The 21cm angular-power spectrum from the dark ages
• Observational constraints on the curvaton model of inflation
• Heating of Baryons due to Scattering with Dark Matter During the Dark Ages
• Stringent Limit on Primordial Magnetic Fields from the Cosmic Microwave Background Radiation
• Silk damping at a redshift of a billion: a new limit on small-scale adiabatic perturbations
• Ultrafast effective multi-level atom method for primordial hydrogen recombination
• CMB spectral distortions from small-scale isocurvature fluctuations
• Signals From the Epoch of Cosmological Recombination
• A comparison of cosmological Boltzmann codes: are we ready for high precision cosmology?
• Limits on isocurvature fluctuations from Boomerang and MAXIMA
• Primordial helium recombination I: feedback, line transfer, and continuum opacity
• Full covariance of CMB and lensing reconstruction power spectra
• CMB Delensing Beyond the B Modes
• A new light on 21 cm intensity fluctuations from the dark ages
• Breaking the spell of Gaussianity: forecasting with higher order Fisher matrices
• Cosmological Perturbations at Second Order and Recombination Perturbed
• Compensated Isocurvature Perturbations and the Cosmic Microwave Background
• CosmoSpec: Fast and detailed computation of the cosmological recombination radiation from hydrogen and helium
• Forecasted 21 cm constraints on compensated isocurvature perturbations
• HYREC-2: a highly accurate sub-millisecond recombination code
• Search for Compensated Isocurvature Perturbations with Planck Power Spectra
• Baryons do trace dark matter 380,000 years after the big bang: Search for compensated isocurvature perturbations with WMAP 9-year data
• On Possible Variation in the Cosmological Baryon Fraction
• The primordial deuterium abundance at z = 2.504 from a high signal-to-noise spectrum of Q1009+2956
• Non-Gaussianities from Perturbing Recombination
• Open and closed CDM isocurvature models contrasted with the CMB data
• Can small-scale baryon inhomogeneities resolve the Hubble tension? An investigation with ACT DR4
• Compensated isocurvature perturbations in the curvaton model
• Power Spectra Based Planck Constraints on Compensated Isocurvature, and Forecasts for LiteBIRD and CORE Space Missions
• Do baryons trace dark matter in the early universe?
• Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature
• Sensitivity forecasts for the cosmological recombination radiation in the presence of foregrounds
• Big Bang Nucleosynthesis Constraint on Baryonic Isocurvature Perturbations
• Large scale distribution of total mass versus luminous matter from Baryon Acoustic Oscillations: First search in the SDSS-III BOSS Data Release 10
• Probing Compensated Isocurvature with the 21-cm Signal during Cosmic Dawn
• Compensated Isocurvature Perturbations in the Galaxy Power Spectrum
• Probing a panoply of curvaton-decay scenarios using CMB data
• Perturbed recombination from inhomogeneous photon injection and application to accreting primordial black holes
• Stability of small-scale baryon perturbations during cosmological recombination