Towards a characterization of X-ray galaxy clusters for cosmology. (arXiv:1907.03806v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kafer_F/0/1/0/all/0/1">Florian K&#xe4;fer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Finoguenov_A/0/1/0/all/0/1">Alexis Finoguenov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eckert_D/0/1/0/all/0/1">Dominique Eckert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanders_J/0/1/0/all/0/1">Jeremy S. Sanders</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reiprich_T/0/1/0/all/0/1">Thomas H. Reiprich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nandra_K/0/1/0/all/0/1">Kirpal Nandra</a>

In the framework of the hierarchical model the intra-cluster medium
properties of galaxy clusters are tightly linked to structure formation, which
makes X-ray surveys well suited for cosmological studies. To constrain
cosmological parameters accurately by use of galaxy clusters in X-ray surveys,
a better understanding of selection effects related to the detection method is
needed. We aim at a better understanding of galaxy cluster morphologies to
include corrections between the different core types and covariances with X-ray
luminosities in selection functions. We stress the morphological deviations
between a newly described surface brightness (SB) profile characterization and
a commonly used single $beta$-model. We investigate a novel approach to
describe SB profiles, where the excess cool-core emission in the galaxy cluster
centres is modelled using wavelet decomposition. Morphological parameters and
the residuals are compared to classical single $beta$-models. Using single
$beta$-models to describe the ensemble of overall SB profiles leads on average
to a non-zero bias ($0.032 pm 0.003$) in the outer part of the clusters, i.e.
a $sim 3%$ systematic difference in the SB at large radii. In addition
$beta$-models show a general trend towards underestimating the flux in the
outskirts for smaller core radii. Fixing the $beta$ parameter to $2/3$ doubles
the bias and increases the residuals from a single $beta$-model up to more
than $40%$. Modelling the core region in the fitting procedure reduces the
impact of these two effects significantly. We find a positive scaling between
shape parameters and temperature, as well as a negative correlation
($sim-0.4$) between extent and luminosity. Our non-parametric analysis of the
self-similar scaled emission measure profiles indicates no systematic core-type
differences of median profiles in the galaxy clusters outskirts.

In the framework of the hierarchical model the intra-cluster medium
properties of galaxy clusters are tightly linked to structure formation, which
makes X-ray surveys well suited for cosmological studies. To constrain
cosmological parameters accurately by use of galaxy clusters in X-ray surveys,
a better understanding of selection effects related to the detection method is
needed. We aim at a better understanding of galaxy cluster morphologies to
include corrections between the different core types and covariances with X-ray
luminosities in selection functions. We stress the morphological deviations
between a newly described surface brightness (SB) profile characterization and
a commonly used single $beta$-model. We investigate a novel approach to
describe SB profiles, where the excess cool-core emission in the galaxy cluster
centres is modelled using wavelet decomposition. Morphological parameters and
the residuals are compared to classical single $beta$-models. Using single
$beta$-models to describe the ensemble of overall SB profiles leads on average
to a non-zero bias ($0.032 pm 0.003$) in the outer part of the clusters, i.e.
a $sim 3%$ systematic difference in the SB at large radii. In addition
$beta$-models show a general trend towards underestimating the flux in the
outskirts for smaller core radii. Fixing the $beta$ parameter to $2/3$ doubles
the bias and increases the residuals from a single $beta$-model up to more
than $40%$. Modelling the core region in the fitting procedure reduces the
impact of these two effects significantly. We find a positive scaling between
shape parameters and temperature, as well as a negative correlation
($sim-0.4$) between extent and luminosity. Our non-parametric analysis of the
self-similar scaled emission measure profiles indicates no systematic core-type
differences of median profiles in the galaxy clusters outskirts.

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