Аннотация
We use the MACSIS hydrodynamical simulations to estimate the extent of gas
clumping in the intracluster medium of massive galaxy clusters and how it
affects the hydrostatic mass bias. By comparing the clumping to the azimuthal
scatter in the emission measure, an observational proxy, we find that they both
increase with radius and are larger in higher-mass and dynamically perturbed
systems. Similar trends are also seen for the azimuthal temperature scatter and
non-thermal pressure fraction, both of which correlate with density
fluctuations, with these values also increasing with redshift. However, in
agreement with recent work, we find only a weak correlation between the
clumping, or its proxies, and the hydrostatic mass bias. To reduce the effect
of clumping in the projected profiles, we compute the azimuthal median
following recent observational studies, and find this reduces the scatter in
the bias. We also attempt to correct the cluster masses by using a non-thermal
pressure term and find over-corrected mass estimates ($1-b=0.86$ to $1-b=1.15$)
from 3D gas profiles but improved mass estimates ($1-b=0.75$ to $1-b=0.85$)
from projected gas profiles. We conclude that the cluster-averaged mass bias is
minimised from applying a non-thermal pressure correction ($1-b=0.85$) with
more modest reductions from selecting clusters that have low clumping
($1-b=0.79$) or are dynamically relaxed ($1-b=0.80$). However, the latter
selection is most effective at minimising the scatter for individual objects.
Such results can be tested with next generation X-ray missions equipped with
high-resolution spectrometers such as Athena.
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