The peculiar velocity field: constraining the tilt of the Universe

Abstract

A large bulk flow, which is in tension with the Lambda Cold Dark Matter ($\Lambda$CDM) cosmological model, has been observed. In this paper, we provide a physically plausible explanation of this bulk flow, based on the assumption that some fraction of the observed dipole in the cosmic microwave background is due to an intrinsic fluctuation, so that the subtraction of the observed dipole leads to a mismatch between the cosmic microwave background (CMB) defined rest frame and the matter rest frame. We investigate a model that takes into account the relative velocity (hereafter the tilted velocity) between the two frames, and develop a Bayesian statistic to explore the likelihood of this tilted velocity. By studying various independent peculiar velocity catalogs, we find that: (1) the magnitude of the tilted velocity $u$ is around 400 km/s, and its direction is close to what is found from previous bulk flow analyses; for most catalogs analysed, u=0 is excluded at about the $2.5\sigma$ level;(2) constraints on the magnitude of the tilted velocity can result in constraints on the duration of inflation, due to the fact that inflation can neither be too long (no dipole effect) nor too short (very large dipole effect); (3) Under the assumption of a super-horizon isocurvature fluctuation, the constraints on the tilted velocity require that inflation lasts at least 6 e-folds longer (at the 95% confidence interval) than that required to solve the horizon problem. This opens a new window for testing inflation and models of the early Universe from observations of large scale structure.

7 pages, 7 figures, match the published version in Phys.Rev.D

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• Reconstructed Density and Velocity Fields from the 2MASS Redshift Survey
• Superhorizon Perturbations and the Cosmic Microwave Background
• Gauging the cosmic microwave background
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Cited by in corpus (30)

• The 6dF Galaxy Velocity Survey: Cosmological constraints from the velocity power spectrum
• Analyzing the Large-Scale Bulk Flow using CosmicFlows4: Increasing Tension with the Standard Cosmological Model
• 2MTF VI. Measuring the velocity power spectrum
• Probing the anisotropic expansion from supernovae and GRBs in a model-independent way
• The Sloan Digital Sky Survey Peculiar Velocity Catalogue
• Improving constraints on the growth rate of structure by modelling the density-velocity cross-correlation in the 6dF Galaxy Survey
• Dipolar modulation in number counts of WISE-2MASS sources
• Probing bulk flow with nearby SNe Ia data
• Evaluating bulk flow estimators for CosmicFlows-4 measurements
• Large-scale Cosmic Flows from Cosmicflows-2 Catalog
• The multipole expansion of the local expansion rate
• Complementarity of Peculiar Velocity Surveys and Redshift Space Distortions for Testing Gravity
• Using peculiar velocity surveys to constrain the growth rate of structure with the wide-angle effect
• Growth-rate measurement with type-Ia supernovae using ZTF survey simulations
• Double-Kasner Spacetime: Peculiar Velocities and Cosmic Jets
• Cosmic Flow Measurement and Mock Sampling Algorithm of Cosmicflows-4 Tully-Fisher Catalogue
• Cosmology with Peculiar Velocities: Observational Effects
• Peculiar Transverse Velocities of Galaxies from Quasar Microlensing. Tentative Estimate of the Peculiar Velocity Dispersion at $z\sim 0.5$
• Probing the rest-frame of the Universe with near-IR cosmic infrared background
• Forecast for growth-rate measurement using peculiar velocities from LSST supernovae
• Friction forces in cosmological models
• Velocities hasten to tell us about the Universe
• Constraining the optical depth of galaxies and velocity bias with cross-correlation between kinetic Sunyaev-Zeldovich effect and peculiar velocity field
• A probabilistic framework for cosmological inference of peculiar velocities
• Statistical effects of the observer's peculiar velocity on source number counts
• Anchors no more: Using peculiar velocities to constrain $H_0$ and the primordial Universe without calibrators
• Cosmic Dipoles from Large-Scale Structure Surveys
• Squared-field cross-correlation between kinetic Sunyaev-Zel'dovich effect and 21-cm intensity mapping
• First constraints on the intrinsic CMB dipole and our velocity with Doppler and aberration
• Galaxy number-count dipole and superhorizon fluctuations