Turning dispersion into signal: density-split analyses of pairwise velocities

Abstract

Pairwise velocities of the large-scale structure encode valuable information about the growth of structure. They can be observed indirectly through redshift-space distortions and the kinetic Sunyaev-Zeldovich effect. Whether it is Gaussian or non-Gaussian, the pairwise velocity has a broad distribution, but the cosmologically useful information lies primarily in the mean -the streaming velocities; the dispersion around the mean is often treated as a nuisance and marginalised over. This reduces the constraining power of our observations. We demonstrate that this is not necessarily the case, provided the underlying physics behind the dispersion is understood. By splitting the halo/galaxy samples according to their density environments and measuring the streaming velocities separately, the total signal-to-noise is several times greater than in conventional global measurements of the pairwise velocity distribution (PVD). This improvement arises because the global PVD is a composite of a series of near-Gaussian distributions with different means and dispersions, each determined by its local density environment. By splitting the data, we avoid cancellation between these opposing velocities, effectively turning the dispersion in the global PVD into a signal. Our findings indicate substantial potential for improving the analysis of PVD observations using the kinetic Sunyaev-Zeldovich effect and redshift-space distortions.

7 pages, 5 figures

References in corpus (33)

• Large-Scale Structure of the Universe and Cosmological Perturbation Theory
• A measurement of the cosmological mass density from clustering in the 2dF Galaxy Redshift Survey
• A test of the nature of cosmic acceleration using galaxy redshift distortions
• Redshift-Space Distortions, Pairwise Velocities and Nonlinearities
• The Quijote simulations
• Evidence of Galaxy Cluster Motions with the Kinematic Sunyaev-Zel'dovich Effect
• Towards an accurate model of the redshift space clustering of halos in the quasilinear regime
• Peculiar velocities of galaxies and clusters
• Beyond BAO: improving cosmological constraints from BOSS with measurement of the void-galaxy cross-correlation
• Density split statistics: Cosmological constraints from counts and lensing in cells in DES Y1 and SDSS data
• Position-dependent power spectrum of the large-scale structure: a novel method to measure the squeezed-limit bispectrum
• Redshift-Space Distortions with the Halo Occupation Distribution II: Analytic Model
• An analytic model for redshift-space distortions
• The Gaussian streaming model and Lagrangian effective field theory
• Linear and nonlinear contributions to pairwise peculiar velocities
• Density split statistics: joint model of counts and lensing in cells
• Streaming velocities as a dynamical estimator of Omega
• The distribution of pairwise peculiar velocities in the nonlinear regime
• Back in the saddle: Large-deviation statistics of the cosmic log-density field
• Dynamics of pairwise motions
• Redshift-space distortions with split densities
• Skewed exponential pairwise velocities from Gaussian initial conditions
• The environmental dependence of clustering in hierarchical models
• A Zeldovich reconstruction method for measuring redshift space distortions using cosmic voids
• An accurate perturbative approach to redshift space clustering of biased tracers in modified gravity
• Modeling peculiar velocities of dark matter halos
• Evolution of the Pairwise Peculiar Velocity Distribution Function in Lagrangian Perturbation Theory
• Pairwise velocities in the Halo Model: Luminosity and Scale Dependence
• Enhancing cosmic shear with the multi-scale lensing PDF
• The Variance and Covariance of Counts-in-Cells Probabilities
• Modeling Pairwise Peculiar Velocity Distribution Function of Dark Matter from Halo Density Profiles
• Baryon Acoustic Oscillations analyses with Density-Split Statistics
• Estimators for the cross-pairwise kSZ effect: forecasts for the dark energy and modified gravity parameters with Simons Observatory and CMB-S4