Compensated Isocurvature Perturbations in the Galaxy Power Spectrum

Abstract

We investigate the potential of the galaxy power spectrum to constrain compensated isocurvature perturbations (CIPs), primordial fluctuations in the baryon density that are compensated by fluctuations in CDM density to ensure an unperturbed total matter density. We show that CIPs contribute to the galaxy overdensity at linear order, and if they are close to scale-invariant, their effects are nearly perfectly degenerate with the local PNG parameter $f_{\mathrm{nl}}$ if they correlate with the adiabatic perturbations. This degeneracy can however be broken by analyzing multiple galaxy samples with different bias parameters, or by taking CMB priors on $f_{\mathrm{nl}}$ into account. Parametrizing the amplitude of the CIP power spectrum as $P_{\sigma \sigma }=A^2{P}_{\mathcal{RR}}$ (where $P_{\mathcal{RR}}$ is the adiabatic power spectrum) we find, for a number of fiducial galaxy samples in a simplified forecast setup, that constraints on $A$, relative to those on $f_{\mathrm{nl}}$, of order ${\sigma }_A/{\sigma }_{f_{\mathrm{nl}}}\approx 1-2$ are achievable for CIPs correlated with adiabatic perturbations, and ${\sigma }_A/{\sigma }_{f_{\mathrm{nl}}}\approx 5$ for the uncorrelated case. These values are independent of survey volume, and suggest that current galaxy data are already able to improve significantly on the tightest existing constraints on CIPs from the CMB. Future galaxy surveys that aim to achieve ${\sigma }_{f_{\mathrm{nl}}}\sim 1$ have the potential to place even stronger bounds on CIPs.

17 pages + references and appendix; 6 figures; 1 table. Comments welcomed! v2 matches version published in JCAP

References in corpus (8)

• Simulating galaxy formation with black hole driven thermal and kinetic feedback
• The imprints of primordial non-gaussianities on large-scale structure: scale dependent bias and abundance of virialized objects
• Measuring primordial non-gaussianity without cosmic variance
• Constraints on primordial non-Gaussianity from 800,000 photometric quasars
• Forecasted 21 cm constraints on compensated isocurvature perturbations
• Large-Scale Structure Observables in General Relativity
• Probing primordial non-Gaussianity via iSW measurements with SKA continuum surveys
• Lensing Bias to CMB Polarization Measurements of Compensated Isocurvature Perturbations

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• Kinetic Sunyaev-Zel'dovich tomography with line-intensity mapping
• Probing Compensated Isocurvature with the 21-cm Signal during Cosmic Dawn
• Uncorrelated Compensated Isocurvature Perturbations from kSZ Tomography
• Phenomenology of a vector-field-induced (and possibly parity breaking) compensated isocurvature perturbation
• Magnetic Fields from Compensated Isocurvature Perturbations
• The intrinsic bispectrum of the CMB from isocurvature initial conditions
• Cosmic voids and BAO with relative baryon-CDM perturbations
• Diagnosing Systematic Effects Using the Inferred Initial Power Spectrum
• Probing small-scale baryon and dark matter isocurvature perturbations with cosmic microwave background anisotropies