The SRG/eROSITA All-Sky Survey: Exploring halo assembly bias with X-ray selected superclusters
arxiv(2024)
摘要
We explore halo assembly bias on cluster scales using large samples of
superclusters. Leveraging the largest-ever X-ray galaxy cluster and
supercluster samples obtained from the first SRG/eROSITA all-sky survey, we
construct two subsamples of galaxy clusters which consist of supercluster
members (SC) and isolated clusters (ISO) respectively. After correcting the
selection effects on redshift, mass, and survey depth, we compute the excess in
the concentration of the intracluster gas of isolated clusters with respect to
supercluster members, defined as δ c_ gas≡ c_
gas,ISO/c_ gas,SC-1, to investigate the environmental effect on the
concentration of clusters, an inference of halo assembly bias on cluster
scales. We find that the average gas mass concentration of isolated clusters is
a few percent higher than that of supercluster members, with a significance of
2σ. The result on δ c_ gas varies with the overdensity ratio
f in supercluster identification, cluster mass proxies, and mass ranges, but
remains positive in all the measurements. We measure slightly larger δ
c_ gas when adopting a higher f in supercluster identification. δ
c_ gas is also larger for low-mass clusters, and almost negligible for
high-mass clusters. We perform weak lensing analyses to compare the total mass
concentration of the two classes and find a similar trend as obtained from gas
mass concentration. Our results are consistent with the prediction of HAB on
cluster scales, where halos located in denser environments are less
concentrated, and this trend is stronger for low-mass halos than for massive
halos. These phenomena can be interpreted by the fact that clusters in denser
environments such as superclusters have experienced more mergers than isolated
clusters in their assembling history.
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