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Discovery of a Ringlike Dark Matter Structure in the Core of the Galaxy
Cluster Cl 0024+17 | | M.J. Jee
; H.C. Ford
; G.D. Illingworth
; R.L. White
; T.J. Broadhurst
; D.A. Coe
; G.R. Meurer
; A. Van Der Wel
; N. Benitez
; J.P. Blakeslee
; R.J. Bouwens
; L.D. Bradley
; R. Demarco
; N.L. Homeier
; A.R. Martel
; S. Mei
; | | Date: |
15 May 2007 | | Subject: | Astrophysics (astro-ph) | | Abstract: | We present a comprehensive mass reconstruction of the rich galaxy cluster Cl
0024+17 at z~0.4 from ACS data, unifying both strong- and weak-lensing
constraints. The weak-lensing signal from a dense distribution of background
galaxies (~120 per square arcmin) across the cluster enables the derivation of
a high-resolution parameter-free mass map. The strongly-lensed objects tightly
constrain the mass structure of the cluster inner region on an absolute scale,
breaking the mass-sheet degeneracy. The mass reconstruction of Cl 0024+17
obtained in such a way is remarkable. It reveals a ringlike dark matter
substructure at r~75" surrounding a soft, dense core at r~50". We interpret
this peculiar sub-structure as the result of a high-speed line-of-sight
collision of two massive clusters 1-2 Gyr ago. Such an event is also indicated
by the cluster velocity distribution. Our numerical simulation with purely
collisionless particles demonstrates that such density ripples can arise by
radially expanding, decelerating particles that originally comprised the
pre-collision cores. Cl 0024+17 can be likened to the bullet cluster 1E0657-56,
but viewed $along$ the collision axis at a much later epoch. In addition, we
show that the long-standing mass discrepancy for Cl 0024+17 between X-ray and
lensing can be resolved by treating the cluster X-ray emission as coming from a
superposition of two X-ray systems. The cluster’s unusual X-ray surface
brightness profile that requires a two isothermal sphere description supports
this hypothesis. | | Source: | arXiv, arxiv.0705.2171 | | Services: | Forum | Review | PDF | Favorites | |
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