Journal
ASTROPHYSICAL JOURNAL
Volume 701, Issue 2, Pages 1336-1346Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/701/2/1336
Keywords
galaxies: clusters: individual (A1689); galaxies: kinematics and dynamics; methods: data analysis
Categories
Funding
- ICRR in Tokyo, Japan
- John Simon GuggenheimMemorial Foundation
- National Science Council of Taiwan [NSC97-2112-M-001-020MY3]
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We examine the dynamics structure of the rich cluster A1689, combining VLT/VIMOS spectroscopy with Subaru/ Suprime-Cam imaging. The radial velocity distribution of similar to 500 cluster members is bounded by a pair of clearly defined velocity caustics, with a maximum amplitude of similar to|4000| km s(-1) at similar or equal to 300 h(-1) kpc, beyond which the amplitude steadily declines, approaching zero velocity at a limiting radius of similar to 2 h(-1) Mpc. We derive the three-dimensional velocity anisotropy and galaxy number density profiles using a model-independent method to solve the Jeans equation, simultaneously incorporating the observed velocity dispersion profile, the galaxy counts from deep Subaru imaging, and our previously derived cluster mass profile from a joint lensing and Xray analysis. The velocity anisotropy is found to be predominantly radial at large radius, becoming increasingly tangential towards the center, in accord with expectations. We also analyze the galaxy data independently of our previous analysis using two different methods: The first is based on a solution of the Jeans equation assuming an Navarro-Frenk-White (NFW) form for the mass distribution, whereas in the second method the caustic amplitude is used to determine the escape velocity. The cluster virial mass derived by both of these dynamical methods is in good agreement with results from our earlier lensing and X-ray analysis. We also confirm the high NFW concentration parameter, with results from both methods combined to yield c(vir) > 13 (1 sigma). The inferred virial radius is consistent with the limiting radius where the caustics approach zero velocity and where the counts of cluster members drop off, suggesting that infall onto A1689 is currently not significant.
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