PROFILES OF DARK MATTER VELOCITY ANISOTROPY IN SIMULATED CLUSTERS
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
- San Diego Supercomputer Center, University of California, San Diego, MC 0505, 10100 Hopkins Drive, La Jolla, CA 92093 (United States)
- Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States)
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)
- Department of Theoretical Physics, University of the Basque Country UPV/EHU, E-48949 Leioa (Spain)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
We report statistical results for dark matter (DM) velocity anisotropy, {beta}, from a sample of some 6000 cluster-size halos (at redshift zero) identified in a {Lambda}CDM hydrodynamical adaptive mesh refinement simulation performed with the ENZO code. These include profiles of {beta} in clusters with different masses, relaxation states, and at several redshifts, modeled both as spherical and triaxial DM configurations. Specifically, although we find a large scatter in the DM velocity anisotropy profiles of different halos (across elliptical shells extending to at least {approx}1.5r{sub vir}), universal patterns are found when these are averaged over halo mass, redshift, and relaxation stage. These are characterized by a very small velocity anisotropy at the halo center, increasing outward to {approx}0.27 and leveling off at {approx}0.2r{sub vir}. Indirect measurements of the DM velocity anisotropy fall on the upper end of the theoretically expected range. Though measured indirectly, the estimations are derived by using two different surrogate measurements-X-ray and galaxy dynamics. Current estimates of the DM velocity anisotropy are based on a very small cluster sample. Increasing this sample will allow theoretical predictions to be tested, including the speculation that the decay of DM particles results in a large velocity boost. We also find, in accord with previous works, that halos are triaxial and likely to be more prolate when unrelaxed, whereas relaxed halos are more likely to be oblate. Our analysis does not indicate that there is significant correlation (found in some previous studies) between the radial density slope, {gamma}, and {beta} at large radii, 0.3 r{sub vir} < r < r{sub vir}.
- OSTI ID:
- 22037005
- Journal Information:
- Astrophysical Journal, Vol. 752, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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