Measuring Transverse Motions for Nearby Galaxy Clusters

Abstract

Measuring the full three-dimensional motions of extra-galactic objects in the Universe presents a seemingly insurmountable challenge. In this paper we investigate the application of a technique to measure tangential motion that has previously only been applied nearby within the Local Group of galaxies, to clusters of galaxies far beyond its borders. We show that mapping the mean line-of-sight motion throughout a galaxy cluster could in principle be used to detect the "perspective rotation" induced by the projection of the cluster's tangential motion into the line-of-sight. The signal will be most prominent for clusters of the largest angular extent, most symmetric intrinsic velocity distribution and surveyed with the largest number of pointings possible. We investigate the feasibility of detecting this signal using three different approaches: measuring line-of-sight motions of individual cluster members; taking spectra of intracluster gas; and mapping distortions of the Cosmic Microwave Background radiation. We conclude that future spectroscopic surveys of 1000's of members of nearby galaxy clusters hold the most promise of measuring cluster tangential motions using this technique.

Accepted for publication in ApJ Letters

References in corpus (7)

• M31 Transverse Velocity and Local Group Mass from Satellite Kinematics
• Systemic Proper Motions of Milky Way Satellites from Stellar Redshifts: the Carina, Fornax, Sculptor and Sextans Dwarf Spheroidals
• Spectroscopic Determination of the Faint End of the Luminosity Function in the Nearby Galaxy Clusters A2199 and Virgo
• Observations of High-Redshift X-Ray Selected Clusters with the Sunyaev-Zel'dovich Array
• Rotation and Turbulence of the Hot ICM in Galaxy Clusters
• Proper Motion of Milky Way Dwarf Spheroidals from Line-of-Sight Velocities
• The velocity--shape alignment of clusters and the kinetic Sunyaev--Zeldovich effect

Cited by in corpus (7)

• Kinetic Sunyaev--Zel'dovich effect in rotating galaxy clusters from MUSIC simulations
• Tests of Gravity with Galaxy Clusters
• Galaxy cluster's rotation
• Probing the Halo From the Solar Vicinity to the Outer Galaxy: Connecting Stars in Local Velocity Structures to Large-Scale Clouds
• Objects Appear Smaller as They Recede: How Proper Motions Can Directly Reveal the Cosmic Expansion, Provide Geometric Distances, and Measure the Hubble Constant
• The Relation Between Transverse and Radial Velocity Distributions for Observations of an Isotropic Velocity Field
• Effect of Composition Gradient on Magnetothermal Instability Modified by Shear and Rotation