The error budget of the Dark Flow measurement

Abstract

We analyze the uncertainties and possible systematics associated with the "Dark Flow" measurements using the cumulative Sunyaev-Zeldovich effect combined with all-sky catalogs of clusters of galaxies. Filtering of all-sky cosmic microwave background (CMB) maps is required to remove the intrinsic cosmological signal down to the limit imposed by cosmic variance. Contributions to the errors come from the remaining cosmological signal, that integrates down with the number of clusters, and the instrumental noise, that scales with the number of pixels; the latter decreases with integration time and is subdominant for the Wilkinson Microwave Anisotropy Probe 5-year data. It is proven both analytically and numerically that the errors for 5-year WMAP data are $\simeq 15\sqrt{3/N_{\mathrm{clusters}}}\mu$K per dipole component. The measured bulk flow velocity is significant at up to the $>99.95$ confidence level, depending on the cluster sample. We discuss different methods to compute error bars and demonstrate that they have biases that would overpredict the errors, as is the case in a recent reanalysis of our earlier results. If the signal is caused by systematic effects present in the data, such systematics must have a dipole pattern, which correlates with cluster X-ray luminosity and is present only at cluster positions. Only contributions from the Sunyaev-Zeldovich effect could provide such contaminants via several potential effects. We discuss such candidates apart from the bulk-motion of the cluster samples and demonstrate that their contributions to our measurements are negligible. (abridged)

ApJ, in press

References in corpus (3)

• A new measurement of the bulk flow of X-ray luminous clusters of galaxies
• Measurement of the electron-pressure profile of galaxy clusters in Wilkinson Microwave Anisotropy Probe (WMAP) 3-year data
• The Statistical Significance of the "Dark Flow"

Cited by in corpus (17)

• Is the Observable Universe Consistent with the Cosmological Principle?
• The kSZ effect as a test of general radial inhomogeneity in LTB cosmology
• Hubble flow variance and the cosmic rest frame
• Measuring the dark flow with public X-ray cluster data
• The Signature of Proper Motion in the Microwave Sky
• Measuring the Galaxy Cluster Bulk Flow from WMAP data
• Measuring the cosmological bulk flow using the peculiar velocities of supernovae
• First measurement of the bulk flow of nearby galaxies using the cosmic microwave background
• Probing the Dark Flow signal in WMAP 9 yr and PLANCK cosmic microwave background maps
• Anisotropy of the galaxy cluster X-ray luminosity-temperature relation
• Measuring our Peculiar Velocity by "Pre-deboosting" the CMB
• Galaxy Cluster Bulk Flows and Collision Velocities in QUMOND
• On the Statistical Significance of the Bulk Flow Measured by the PLANCK Satellite
• Probing the Universe's Tilt with the Cosmic Infrared Background Dipole
• Explaining Excess Dipole in NVSS Data Using Superhorizon Perturbation
• Probing the rest-frame of the Universe with near-IR cosmic infrared background
• Statistics of WMAP ILC map temperature fluctuations towards distant radio galaxies