Observational biases in Lagrangian reconstructions of cosmic velocity fields

Abstract

Lagrangian reconstruction of large-scale peculiar velocity fields can be strongly affected by observational biases. We develop a thorough analysis of these systematic effects by relying on specially selected mock catalogues. For the purpose of this paper, we use the MAK reconstruction method, although any other Lagrangian reconstruction method should be sensitive to the same problems. We extensively study the uncertainty in the mass-to-light assignment due to luminosity incompleteness, and the poorly-determined relation between mass and luminosity. The impact of redshift distortion corrections is analyzed in the context of MAK and we check the importance of edge and finite-volume effects on the reconstructed velocities. Using three mock catalogues with different average densities, we also study the effect of cosmic variance. In particular, one of them presents the same global features as found in observational catalogues that extend to 80 Mpc/h scales. We give recipes, checked using the aforementioned mock catalogues, to handle these particular observational effects, after having introduced them into the mock catalogues so as to quantitatively mimic the most densely sampled currently available galaxy catalogue of the nearby universe. Once biases have been taken care of, the typical resulting error in reconstructed velocities is typically about a quarter of the overall velocity dispersion, and without significant bias. We finally model our reconstruction errors to propose an improved Bayesian approach to measure Omega_m in an unbiased way by comparing the reconstructed velocities to the measured ones in distance space, even though they may be plagued by large errors. We show that, in the context of observational data, a nearly unbiased estimator of Omega_m may be built using MAK reconstruction.

29 pages, 21 figures, 6 tables, Accepted by MNRAS on 2007 October 2. Received 2007 September 30; in original form 2007 July 24

References in corpus (6)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Cosmological Constraints from the SDSS Luminous Red Galaxies
• Improving Cosmological Distance Measurements by Reconstruction of the Baryon Acoustic Peak
• The Tully-Fisher Relation and Its Residuals for a Broadly Selected Sample of Galaxies
• Reconstructed Density and Velocity Fields from the 2MASS Redshift Survey
• On the luminosity function of galaxies in groups in the Sloan Digital Sky Survey

Cited by in corpus (14)

• Simulations of ultra-high Energy Cosmic Rays in the local Universe and the origin of Cosmic Magnetic Fields
• Deriving accurate peculiar velocities (even at high redshift)
• Rejuvenating Power Spectra II: the Gaussianized galaxy density field
• Cosmic Structure and Dynamics of the Local Universe
• Mapping the real space distributions of galaxies in SDSS DR7: I. Two Point Correlation Functions
• The Cosmic V-Web
• I- A hydrodynamical CLONE of the Virgo cluster of galaxies to confirm observationally-driven formation scenarios
• Cosmic Velocity Field Reconstruction Using AI
• Removing BAO-peak Shifts with Local Density Transforms
• Virgo: an unlikely cluster of galaxies because of its environment
• Predicting Structures in the Zone of Avoidance
• Cosmic Web & Caustic Skeleton: non-linear Constrained Realizations -- 2D case studies
• Efficiently estimating mean, uncertainty and unconstrained large scale fraction of local Universe simulations with paired fixed fields
• Probing Time-Varying Dark Energy with DESI: The Crucial Role of Precision Matter Density (Ω_{m0}) Measurements