Gaia: a Window to Large Scale Flows

Abstract

Using redshifts as a proxy for galaxy distances, estimates of the 2D transverse peculiar velocities of distant galaxies could be obtained from future measurements of proper motions. We provide the mathematical framework for analyzing 2D transverse motions and show that they offer several advantages over traditional probes of large scale motions. They are completely independent of any intrinsic relations between galaxy properties, hence they are essentially free of selection biases. They are free from homogeneous and inhomogeneous Malmquist biases that typically plague distance indicator catalogs. They provide additional information to traditional probes which yield line-of-sight peculiar velocities only. Further, because of their 2D nature, fundamental questions regarding vorticity of large scale flows can be addressed. Gaia for example is expected to provide proper motions of at least bright galaxies with high central surface brightness, making proper motions a likely contender traditional probes based on current and future distance indicator measurements.

matches published version

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Cited by in corpus (11)

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• Kinematic Morphology of Large-scale Structure: Evolution from Potential to Rotational Flow
• Joint velocity and density reconstruction of the Universe with nonlinear differentiable forward modeling
• Objects Appear Smaller as They Recede: How Proper Motions Can Directly Reveal the Cosmic Expansion, Provide Geometric Distances, and Measure the Hubble Constant
• Uneven flows: On cosmic bulk flows, local observers, and gravity
• Two is better than one: joint statistics of density and velocity in concentric spheres as a cosmological probe
• Cosmology with extragalactic proper motions: harmonic formalism, estimators, and forecasts
• A direct probe of cosmological power spectra of the peculiar velocity field and the gravitational lensing magnification from photometric redshift surveys
• The Relation Between Transverse and Radial Velocity Distributions for Observations of an Isotropic Velocity Field
• Toward a Measurement of the Transverse Peculiar Velocity of Galaxy Pairs
• Dynamics of The Tranquil Cosmic Web