C.D.S. - SIMBAD4 rel 1.7 - 2021.02.28CET20:39:13

2005A&A...433..777P - Astronomy and Astrophysics, volume 433, 777-785 (2005/4-3)

Further evidence for a merger in Abell 2218 from an XMM-Newton observation.


Abstract (from CDS):

The galaxy cluster Abell 2218, at z=0.171, is well-known for the discrepancy between mass estimates derived from X-ray and strong lensing analyses. With the present XMM-Newton observation, we are able to trace the gas density and temperature profiles out to a radius of ∼1400h70–1kpc (approximately the virial radius of the cluster). The overall surface brightness profile is well fitted over three orders of magnitude with a simple β-model with a core radius of 0.95' and β=0.63. The projected temperature profile declines steeply with radius (by ∼ 50%), and is well described by a polytrope with parameters t0=8.09keV and γ=1.15. The temperature map shows a pronounced peak in the central arcminute, where the temperature rises by a factor of two (from ∼5 to ∼10keV). The mass profile, calculated assuming hydrostatic equilibrium and spherical symmetry, is best fitted with a King approximation to an isothermal sphere, implying a dark matter distribution with a central core, in contrast with the cusped cores found in more obviously relaxed clusters. The X-ray mass is approximately two times less than the strong lensing mass at r∼80h50–1kpc, although the agreement between X-ray and weak lensing mass measurements at larger radius (r∼400h50–1kpc) is slightly better. While the X-ray total mass estimates can vary by 30 per cent depending on the mass model, all measurements are significantly lower than the corresponding total mass from optical measurements. Given the X-ray results indicating considerable disturbance of the intracluster gas, leading to a probable violation of the assumption of hydrostatic equilibrium, and the observed substructure in the optical, suggesting a line-of-sight merger, it is unlikely that the different mass estimates of this cluster can be reconciled, at least with standard modelling assumptions.

Abstract Copyright:

Journal keyword(s): galaxies: clusters: individual: A2218 - galaxies: intergalactic medium - cosmology: observations - cosmolog: dark matter - X-rays: galaxies: clusters

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 ZwCl 0024+1652 ClG 00 26 36.0 +17 08 36     18.35     ~ 608 1
2 ACO 1698 ClG 13 14 16.4165 -07 02 28.310           ~ 14 0
3 ACO 2218 ClG 16 35 54.0 +66 13 00           ~ 782 1

    Equat.    Gal    SGal    Ecl

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