On the recovery of Local Group motion from galaxy redshift surveys

Abstract

There is a $\sim 150km{s}^{-1}$ discrepancy between the measured motion of the Local Group of galaxies (LG) with respect to the CMB and the linear theory prediction based on the gravitational force field of the large scale structure in full-sky redshift surveys. We perform a variety of tests which show that the LG motion cannot be recovered to better than $150-200km{s}^{-1}$ in amplitude and within a $\approx 10^{\circ }$ in direction. The tests rely on catalogs of mock galaxies identified in the Millennium simulation using semi-analytic galaxy formation models. We compare these results to the $K_s=11.75$ Two-Mass Galaxy Redshift Survey, which provides the deepest, widest and most complete spatial distribution of galaxies available so far. In our analysis we use a new, concise relation for deriving the LG motion and bulk flow from the true distribution of galaxies in redshift space. Our results show that the main source of uncertainty is the small effective depth of surveys like the 2MRS that prevents a proper sampling of the large scale structure beyond $\sim 100h^{-1}Mpc$. Deeper redshift surveys are needed to reach the "convergence scale" of $\approx 250h^{-1}Mpc$ in a $\Lambda$CDM universe. Deeper survey would also mitigate the impact of the "Kaiser rocket" which, in a survey like 2MRS, remains a significant source of uncertainty. Thanks to the quiet and moderate density environment of the LG, purely dynamical uncertainties of the linear predictions are subdominant at the level of $\sim 90km{s}^{-1}$. Finally, we show that deviations from linear galaxy biasing and shot noise errors provide a minor contribution to the total error budget.

14 pages, 7 figures

References in corpus (5)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
• The hierarchical formation of the brightest cluster galaxies
• 2MASS Photometric Redshift catalog: a comprehensive three-dimensional census of the whole sky
• The PSCz Dipole Revisited
• Towards the optimal window for the 2MASS dipole

Cited by in corpus (24)

• The 6dF Galaxy Survey: Bulk Flows on $50-70h^{-1}$ Mpc scales
• Cosmic Bulk Flow and the Local Motion from Cosmicflows-2
• The observed galaxy power spectrum in General Relativity
• COSMIC BIRTH: Efficient Bayesian Inference of the Evolving Cosmic Web from Galaxy Surveys
• 2MTF V. Cosmography, Beta, and the residual bulk flow
• Missing baryons traced by the galaxy luminosity density in the large-scale WHIM filaments
• The clustering of radio galaxies: biasing and evolution versus stellar mass
• Velocity-Density Correlations from the cosmicflows-3 Distance Catalog and the 2MASS Redshift Survey
• On the perturbation of the luminosity distance by peculiar motions
• The Clustering of Galaxies in the Completed SDSS-III Baryon Oscillation Spectroscopic Survey: Cosmic Flows and Cosmic Web from Luminous Red Galaxies
• The VIMOS Public Extragalactic Redshift Survey (VIPERS). Measuring nonlinear galaxy bias at z~0.8
• Assessing the accuracy of cosmological parameters estimated from velocity -- density comparisons via simulations
• Cosmic flows and the expansion of the Local Universe from nonlinear phase-space reconstructions
• Generalisation of the Kaiser Rocket effect in general relativity in the wide-angle galaxy 2-point correlation function
• An Inconsistency in standard Maximum Likelihood Estimation of Bulk Flows
• Unveiling the largest structures in the nearby Universe: Discovery of the Quipu superstructure
• Performance study of Lagrangian methods: reconstruction of large scale peculiar velocities and baryonic acoustic oscillations
• Non-linear density-velocity dynamics in $f(R)$ gravity from spherical collapse
• Mapping the Cosmic Web with the largest all-sky surveys
• Re-examination of Large Scale Structure and Cosmic Flows
• The Velocity Field Olympics: Assessing velocity field reconstructions with direct distance tracers
• Dynamics of The Tranquil Cosmic Web
• The Kaiser-Rocket effect: three decades and counting
• First constraints on the intrinsic CMB dipole and our velocity with Doppler and aberration