Studying the Peculiar Velocity Bulk Flow in a Sparse Survey of Type-Ia SNe

Abstract

Studies of the peculiar velocity bulk flow based on different tools and datasets have been consistent so far in their estimation of the direction of the flow, which also happens to lie in close proximity to several features identified in the cosmic microwave background, providing motivation to use new compilations of type-Ia supernovae measurements to pinpoint it with better accuracy and up to higher redshift. Unfortunately, the peculiar velocity field estimated from the most recent Union2.1 compilation suffers from large individual errors, poor sky coverage and low redshift-volume density. We show that as a result, any naive attempt to calculate the best-fit bulk flow and its significance will be severely biased. Instead, we introduce an iterative method which calculates the amplitude and the scatter of the direction of the best-fit bulk flow as deviants are successively removed and take into account the sparsity of the data when estimating the significance of the result. Using 200 supernovae up to a redshift of z=0.2, we find that while the amplitude of the bulk flow is marginally consistent with the value expected in a LCDM universe given the large bias, the scatter of the direction is significantly low (at >= 99.5 C.L.) when compared to random simulations, supporting the quest for a cosmological origin.

7 pages, 6 figures; typos fixed; clarifications made; important references added

References in corpus (10)

• Improved Cosmological Constraints from New, Old and Combined Supernova Datasets
• Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
• The peculiar velocity field: constraining the tilt of the Universe
• The Velocity Field of the Local Universe from Measurements of Type Ia Supernovae
• Cosmic bulk flows on 50 {h}^{-1}Mpc scales: A Bayesian hyper-parameter method and multishells likelihood analysis
• Current Status Of Velocity Field Surveys: A Consistency Check
• One Thousand and One Clusters: Measuring the Bulk Flow with the Planck ESZ and X-Ray Selected Galaxy Cluster Catalogs
• Giant Rings in the CMB Sky
• LCDM: Triumphs, Puzzles and Remedies
• Linear theory and velocity correlations of clusters

Cited by in corpus (25)

• Dark energy two decades after: Observables, probes, consistency tests
• Testing $\Lambda$CDM at the lowest redshifts with SN Ia and galaxy velocities
• Probing the isotropy of cosmic acceleration traced by Type Ia supernovae
• Analyzing the Large-Scale Bulk Flow using CosmicFlows4: Increasing Tension with the Standard Cosmological Model
• Deriving accurate peculiar velocities (even at high redshift)
• Observational constraints on the deceleration parameter in a tilted universe
• Probing the anisotropic expansion from supernovae and GRBs in a model-independent way
• The 6dF Galaxy Survey: Fundamental Plane Data
• 2MTF IV. A bulk flow measurement of the local Universe
• Probing the Dark Flow signal in WMAP 9 yr and PLANCK cosmic microwave background maps
• Dipolar modulation in number counts of WISE-2MASS sources
• Isotropy of low redshift type Ia Supernovae: A Bayesian analysis
• Is there evidence for anomalous dipole anisotropy in the large-scale structure?
• Extensive search for bias in SNIa data
• Constraining the local variance of $H_0$ from directional analyses
• How does the grouping scheme affect the Wiener Filter reconstruction of the local Universe?
• Detectability of Cosmic Dark Flow in the Type Ia Supernova Redshift-Distance Relation
• Explaining Excess Dipole in NVSS Data Using Superhorizon Perturbation
• Uneven flows: On cosmic bulk flows, local observers, and gravity
• Limits on Entanglement Effects in the String Landscape from Planck and BICEP/Keck Data
• Is the local Hubble flow consistent with concordance cosmology?
• The Polarization Signature of Local Bulk Flows
• The Low Redshift survey at Calar Alto (LoRCA)
• Constraints on the birth of the universe and origin of cosmic dark flow
• Gravitational potential wells and the cosmic bulk flow