Cosmology with Peculiar Velocities: Observational Effects

Abstract

In this paper we investigate how observational effects could possibly bias cosmological inferences from peculiar velocity measurements. Specifically, we look at how bulk flow measurements are compared with theoretical predictions. Usually bulk flow calculations try to approximate the flow that would occur in a sphere around the observer. Using the Horizon Run 2 simulation we show that the traditional methods for bulk flow estimation can overestimate the magnitude of the bulk flow for two reasons: when the survey geometry is not spherical (the data do not cover the whole sky), and when the observations undersample the velocity distributions. Our results may explain why several bulk flow measurements found bulk flow velocities that seem larger than those expected in standard ΛCDM cosmologies. We recommend a different approach when comparing bulk flows to cosmological models, in which the theoretical prediction for each bulk flow measurement is calculated specifically for the geometry and sampling rate of that survey. This means that bulk flow values will not be comparable between surveys, but instead they are comparable with cosmological models, which is the more important measure.

11 pages, 5 figures. Accepted for publication in MNRAS

References in corpus (37)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Efficient Computation of CMB anisotropies in closed FRW models
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• Improved Distances to Type Ia Supernovae with Multicolor Light Curve Shapes: MLCS2k2
• Renormalized Cosmological Perturbation Theory
• CMB power spectrum parameter degeneracies in the era of precision cosmology
• Consistently Large Cosmic Flows on Scales of 100 Mpc/h: a Challenge for the Standard LCDM Cosmology
• A measurement of large-scale peculiar velocities of clusters of galaxies: results and cosmological implications
• Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field
• Cosmic flows in the nearby universe from Type Ia Supernovae
• A critical look at cosmological perturbation theory techniques
• Probing the anisotropic local universe and beyond with SNe Ia data
• Cosmic Flows on 100 Mpc/h Scales: Standardized Minimum Variance Bulk Flow, Shear and Octupole Moments
• The effect of peculiar velocities on supernova cosmology
• The cosmological bulk flow: consistency with $\Lambda$CDM and $z\approx 0$ constraints on ${\sigma }_8$ and $\gamma$
• Measuring cosmic bulk flows with Type Ia Supernovae from the Nearby Supernova Factory
• The 6dF Galaxy Survey: Bulk Flows on $50-70h^{-1}$ Mpc scales
• The New Horizon Run Cosmological N-Body Simulations
• The Challenge of the Largest Structures in the Universe to Cosmology
• Cosmic Bulk Flow and the Local Motion from Cosmicflows-2
• The peculiar velocity field: constraining the tilt of the Universe
• Planck intermediate results. XIII. Constraints on peculiar velocities
• The Velocity Field of the Local Universe from Measurements of Type Ia Supernovae
• Measuring the Galaxy Cluster Bulk Flow from WMAP data
• Measuring the cosmological bulk flow using the peculiar velocities of supernovae
• Cosmic bulk flows on 50 {h}^{-1}Mpc scales: A Bayesian hyper-parameter method and multishells likelihood analysis
• 2MTF IV. A bulk flow measurement of the local Universe
• First measurement of the bulk flow of nearby galaxies using the cosmic microwave background
• An estimation of local bulk flow with the maximum-likelihood method
• No evidence for bulk velocity from type Ia supernovae
• Large-scale Cosmic Flows from Cosmicflows-2 Catalog
• An improved model for the nonlinear velocity power spectrum
• Detected fluctuations in SDSS LRG magnitudes: Bulk flow signature or systematic?
• Local gravitational redshifts can bias cosmological measurements
• Bulk flow of halos in ΛCDM simulation
• An Unbiased Method of Modeling the Local Peculiar Velocity Field with Type Ia Supernovae
• Tracing the cosmic velocity field at z ~ 0.1 from galaxy luminosities in the SDSS DR7

Cited by in corpus (9)

• The Local Perspective on the Hubble Tension: Local Structure Does Not Impact Measurement of the Hubble Constant
• Evaluating bulk flow estimators for CosmicFlows-4 measurements
• The Redshift-Space Momentum Power Spectrum I: Optimal Estimation From Peculiar Velocity Surveys
• 2MTF - VII. 2MASS Tully-Fisher survey final data release: distances for 2,062 nearby spiral galaxies
• Bulk flow in the combined 2MTF and 6dFGSv surveys
• Uneven flows: On cosmic bulk flows, local observers, and gravity
• Field-level simulation-based inference with galaxy catalogs: the impact of systematic effects
• Gaussianization of peculiar velocities and bulk flow measurement
• Cross-correlating radial peculiar velocities and CMB lensing convergence