Neural network reconstruction of density and velocity fields from the 2MASS Redshift Survey

Abstract

We reconstruct the 3D matter density and peculiar velocity fields in the local Universe up to a distance of 200$h^{-1}$Mpc from the Two-Micron All-Sky Redshift Survey (2MRS), using a neural network (NN). We employed an NN with a U-net autoencoder architecture and a weighted mean squared error loss function trained separately to output either the density or velocity field for a given input grid of galaxy number counts. The NN was trained on mocks derived from the Quijote N-body simulations, incorporating redshift-space distortions (RSDs), galaxy bias, and selection effects closely mimicking the characteristics of 2MRS. The trained NN was benchmarked against a standard Wiener filter (WF) on a validation set of mocks before applying it to 2MRS. The NN reconstructions effectively approximate the mean posterior estimate of the true density and velocity fields conditioned on the observations. They consistently outperform the WF in terms of reconstruction accuracy and effectively capture the nonlinear relation between velocity and density. The NN-reconstructed bulk flow of the total survey volume exhibits a significant correlation with the true mock bulk flow, demonstrating that the NN is sensitive to information on super-survey scales encoded in the RSDs. When applied to 2MRS, the NN successfully recovers the main known clusters, some of which are partially in the Zone of Avoidance. The reconstructed bulk flows in spheres of different radii less than 100$h^{-1}$Mpc are in good agreement with a previous 2MRS analysis that required an additional external bulk flow component inferred from directly observed peculiar velocities. The NN-reconstructed peculiar velocity of the Local Group closely matches the observed Cosmic Microwave Background dipole in amplitude and Galactic latitude, and only deviates by 18${}^{\circ }$ in longitude. The NN-reconstructed fields are publicly available.

16 pages, 9 figures, 2 tables. Reconstructed fields available at https://github.com/rlilow/2MRS-NeuralNet . Changes in v2: added and updated references, slightly extended explanations and discussions in sections 3 and 6.2, minor language editing to follow A&A style. v2 matches A&A publication

References in corpus (38)

• A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• The Pantheon+ Analysis: Cosmological Constraints
• Cosmic Growth History and Expansion History
• The 2MASS Redshift Survey - Description and Data Release
• Cosmicflows-3
• Fingers of God
• The Quijote simulations
• Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field
• Cosmic flows in the nearby universe from Type Ia Supernovae
• Wiener Reconstruction of The Large Scale Structure
• Reconstructed Density and Velocity Fields from the 2MASS Redshift Survey
• Local Gravity versus Local Velocity: Solutions for $\beta$ and nonlinear bias
• Reconstruction of the early Universe as a convex optimization problem
• Physical Bayesian modelling of the non-linear matter distribution: new insights into the Nearby Universe
• Joint analysis of 6dFGS and SDSS peculiar velocities for the growth rate of cosmic structure and tests of gravity
• Cosmic flows in the nearby Universe: new peculiar velocities from SNe and cosmological constraints
• The Pantheon+ Analysis: Evaluating Peculiar Velocity Corrections in Cosmological Analyses with Nearby Type Ia Supernovae
• Time-analyticity of Lagrangian particle trajectories in ideal fluid flow
• On the least action principle in cosmology
• The velocity field of 2MRS Ks=11.75 galaxies: constraints on beta and bulk flow from the luminosity function
• Wiener Reconstruction of the IRAS 1.2Jy Galaxy Redshift Survey: Cosmographical Implications
• The Mira-Titan Universe IV. High Precision Power Spectrum Emulation
• COSMIC BIRTH: Efficient Bayesian Inference of the Evolving Cosmic Web from Galaxy Surveys
• Galaxy power-spectrum responses and redshift-space super-sample effect
• Constrained realizations of 2MRS density and peculiar velocity fields: growth rate and local flow
• On density and velocity fields and beta from the IRAS PSCz survey
• Peculiar-velocity cosmology with Types Ia and II supernovae
• The 2MASS Redshift Survey in the Zone of Avoidance
• The impact of large-scale tides on cosmological distortions via redshift-space power spectrum
• Reconstructing Cosmological Initial Conditions from Late-Time Structure with Convolutional Neural Networks
• A comparison of the galaxy peculiar velocity field with the PSCz gravity field-- A Bayesian hyper-parameter method
• Reconstructing the cosmological density and velocity fields from redshifted galaxy distributions using V-net
• Large-scale density and velocity field reconstructions with neural networks
• Effective cosmic density field reconstruction with convolutional neural network
• Cosmic Velocity Field Reconstruction Using AI
• Local Primordial Non-Gaussianities and Super-Sample Variance
• Beyond boundaries of redshift surveys: assessing mass fluctuations on "super-survey" scales

Cited by in corpus (4)

• Unveiling the largest structures in the nearby Universe: Discovery of the Quipu superstructure
• The Velocity Field Olympics: Assessing velocity field reconstructions with direct distance tracers
• AVISM: Algorithm for Void Identification in coSMology
• From Redshift to Real Space: Combining Linear Theory With Neural Networks