Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 758, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/758/1/L16
Keywords
galaxies: clusters: general; galaxies: kinematics and dynamics
Categories
Funding
- Danish National Research Foundation
- Instrument Center for Danish Astrophysics
- NASA [PF9-00068]
- U.S. Department of Energy [DE-AC02-76SF00515]
- Division Of Physics
- Direct For Mathematical & Physical Scien [1125897] Funding Source: National Science Foundation
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Measurements of galaxy cluster kinematics are important in understanding the dynamical state and evolution of clusters of galaxies, as well as constraining cosmological models. While it is well established that clusters exhibit non-spherical geometries, evident in the distribution of galaxies on the sky, azimuthal variations of galaxy kinematics within clusters have yet to be observed. Here we measure the azimuthal dependence of the line-of-sight velocity dispersion profile in a stacked sample of 1743 galaxy clusters from the Sloan Digital Sky Survey (SDSS). The clusters are drawn from the SDSS DR8 redMaPPer catalog. We find that the line-of-sight velocity dispersion of galaxies lying along the major axis of the central galaxy is larger than those that lie along the minor axis. This is the first observational detection of anisotropic kinematics of galaxies in clusters. We show that the result is consistent with predictions from numerical simulations. Furthermore, we find that the degree of projected anisotropy is strongly dependent on the line-of-sight orientation of the galaxy cluster, opening new possibilities for assessing systematics in optical cluster finding.
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