1 research outputs found
Resolving the discrepancy between lensing and X-ray mass estimates of the complex galaxy cluster Abell 1689
There is a long-standing discrepancy between galaxy cluster masses determined
from X-ray and gravitational lensing observations of which Abell 1689 is a
well-studied example. In this work we take advantage of 180 ks of Chandra X-ray
observations and a new weak gravitational study based on a Hubble Space
Telescope mosaic covering the central 1.8 Mpc x 1.4 Mpc to eliminate the mass
discrepancy. In contrast to earlier X-ray analyses where the very circular
surface brightness has been inferred as Abell 1689 being spherically symmetric
and in hydrostatic equilibrium, a hardness ratio map analysis reveals a regular
and symmetric appearing main clump with a cool core plus some substructure in
the North Eastern part of the cluster. The gravitational lensing mass model
supports the interpretation of Abell 1689 being composed of a main clump, which
is possibly a virialized cluster, plus some substructure. In order to avoid
complications and mis-interpretations due to X-ray emission from the
substructure, we exclude it from the mass reconstruction. Comparing X-ray and
lensing mass profiles of the regular main part only, shows no significant
discrepancy between the two methods and the obtained mass profiles are
consistent over the full range where the mass can be reconstructed from X-rays
(out to approx. 1 Mpc). The obtained cluster mass within approx. 875 kpc
derived from X-rays alone is 6.4 plus/minus 2.1 x 10^14 solar masses compared
to a weak lensing mass of 8.6 plus/minus 3.0 x 10^14 solar masses within the
same radius.Comment: 9 pages, 10 figures, accepted by Ap