Evaluating bulk flow estimators for CosmicFlows-4 measurements

Abstract

For over a decade there have been contradictory claims in the literature about whether the local bulk flow motion of galaxies is consistent or in tension with the $\Lambda$CDM model. While it has become evident that systematics affect bulk flow measurements, systematics in the estimators have not been widely investigated. In this work, we thoroughly evaluate the performance of four estimator variants, including the Kaiser maximum likelihood estimator (MLE) and the minimum variance estimator (MVE). We find that these estimators are unbiased, however their precision may be strongly correlated with the survey geometry. Small biases in the estimators can be present leading to underestimated bulk flows, which we suspect are due to the presence of non-linear peculiar velocities. The uncertainty assigned to the bulk flows from these estimators is typically underestimated, which leads to an overestimate of the tension with $\Lambda$CDM. We estimate the bulk flow for the CosmicFlows-4 data and use mocks to ensure the uncertainties are appropriately accounted for. Using the MLE we find a bulk flow amplitude of $408\pm 165{\mathrm{kms}}^{-1}$ at a depth of $49\mathrm{Mpc}{h}^{-1}$, in reasonable agreement with $\Lambda$CDM. However using the MVE which can probe greater effective depths, we find an amplitude of $428\pm 108{\mathrm{kms}}^{-1}$ at a depth of $173\mathrm{Mpc}{h}^{-1}$, in tension with the model, having only a 0.11% probability of obtaining a larger ${\chi }^2$. These measurements appear directed towards the Great Attractor region where more data may be needed to resolve tensions.

References in corpus (42)

• Astropy: A Community Python Package for Astronomy
• In the Realm of the Hubble tension $-$ a Review of Solutions
• The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures
• KiDS-1000 Cosmology: Multi-probe weak gravitational lensing and spectroscopic galaxy clustering constraints
• The Arecibo Legacy Fast ALFA Survey: The alpha.40 HI Source Catalog, its Characteristics and their Impact on the Derivation of the HI Mass Function
• The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
• Cosmicflows-3
• The Arecibo Legacy Fast ALFA Survey: The ALFALFA Extragalactic HI Source Catalog
• A Digital Archive of HI 21 cm Line Spectra of Optically-targeted Galaxies
• Cosmological Constraints from Measurements of Type Ia Supernovae discovered during the first 1.5 years of the Pan-STARRS1 Survey
• 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
• Toward a New Geometric Distance to the Active Galaxy NGC 4258. III. Final Results and the Hubble Constant
• Cosmic Flows on 100 Mpc/h Scales: Standardized Minimum Variance Bulk Flow, Shear and Octupole Moments
• The 6dF Galaxy Survey: Peculiar Velocity Field and Cosmography
• Cosmicflows-4
• Joint analysis of 6dFGS and SDSS peculiar velocities for the growth rate of cosmic structure and tests of gravity
• The cosmological bulk flow: consistency with $\Lambda$CDM and $z\approx 0$ constraints on ${\sigma }_8$ and $\gamma$
• Cosmological implications of the anisotropy of ten galaxy cluster scaling relations
• Analyzing the Large-Scale Bulk Flow using CosmicFlows4: Increasing Tension with the Standard Cosmological Model
• The Extragalactic Distance Database: All Digital HI Profile Catalog
• Cosmicflows-4: The Catalog of ~10000 Tully-Fisher Distances
• The 6dF Galaxy Survey: Bulk Flows on $50-70h^{-1}$ Mpc scales
• Cosmic Bulk Flow and the Local Motion from Cosmicflows-2
• The Redshift Space Momentum Power Spectrum II: measuring the growth rate from the combined 2MTF and 6dFGSv surveys
• The peculiar velocity field: constraining the tilt of the Universe
• Improving Cosmological Distance Measurements Using Twin Type Ia Supernovae
• Discovery of a supercluster in the ZOA in Vela
• An Unbiased Estimator of Peculiar Velocity with Gaussian Distributed Errors for Precision Cosmology
• 2MTF IV. A bulk flow measurement of the local Universe
• Structures in the Great Attractor Region
• An estimation of local bulk flow with the maximum-likelihood method
• Large-scale Cosmic Flows from Cosmicflows-2 Catalog
• Determination of the large scale volume weighted halo velocity bias in simulations
• Bulk flow in the combined 2MTF and 6dFGSv surveys
• Easily Interpretable Bulk Flows: Continuing Tension with the Standard Cosmological Model
• Testing the minimum variance method for estimating large-scale velocity moments
• From Cosmicflows distance moduli to unbiased distances and peculiar velocities
• On methods of estimating cosmological bulk flows
• Cosmic Flow Measurement and Mock Sampling Algorithm of Cosmicflows-4 Tully-Fisher Catalogue
• Cosmology with Peculiar Velocities: Observational Effects
• An Inconsistency in standard Maximum Likelihood Estimation of Bulk Flows

Cited by in corpus (28)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• $\Lambda$CDM Tensions: Localising Missing Physics through Consistency Checks
• A simultaneous solution to the Hubble tension and observed bulk flow within 250 $h^{-1}$ Mpc
• An effective description of Laniakea: impact on cosmology and the local determination of the Hubble constant
• Large-scale motions and growth rate from forward-modelling Tully-Fisher peculiar velocities
• Measuring Hubble constant in an anisotropic extension of $\Lambda$CDM model
• The redshift dependence of the inferred $H_0$ in a local void solution to the Hubble tension
• Cosmological foundations revisited with Pantheon+
• Bulk Flow Motion Detection in the Local Universe with Pantheon$+$ Type Ia Supernovae
• Testing the local void hypothesis using baryon acoustic oscillation measurements over the last twenty years
• Anisotropy in Pantheon+ supernovae
• Testing anisotropic Hubble expansion
• Reassessment of the dipole in the distribution of quasars on the sky
• Revisiting the large-scale CMB anomalies: The impact of the SZ signal from the Local Universe
• Big Bang in Dipole Cosmology
• Testing the local supervoid solution to the Hubble tension with direct distance tracers
• Constraints on the Hubble and matter density parameters with and without modelling the CMB anisotropies
• The multi-wavelength Tully-Fisher relation in the TNG50 cosmological simulation
• The Velocity Field Olympics: Assessing velocity field reconstructions with direct distance tracers
• Dispersion in the Hubble-Lemaître constant measurements from gravitational clustering
• In search for the Local Universe dynamical homogeneity scale with CF4++ peculiar velocities
• No evidence for local $H_0$ anisotropy from Tully--Fisher or supernova distances
• A Relativistic Scalar Model for Fractional Interaction between Dark Matter and Gravity
• More power on large scales
• Exploring the cosmic microwave background dipole direction using gamma-ray bursts
• Encyclopedia of Astrophysics: The Expanding Universe
• Confirming the uniformity of the Hubble flow with Pantheon+ Supernovae
• An effective $\mathbf{\Lambda }$-Szekeres modelling of the local Universe with Cosmicflows-4