LoCuSS: The splashback radius of massive galaxy clusters and its
  dependence on cluster merger history
  We present the direct detection of the splashback feature using the sample of
massive galaxy clusters from the Local Cluster Substructure Survey (LoCuSS).
This feature is clearly detected (above $5\sigma$) in the stacked luminosity
density profile obtained using the K-band magnitudes of spectroscopically
confirmed cluster members. We obtained the best-fit model by means of Bayesian
inference, which ranked models including the splashback feature as more
descriptive of the data with respect to models that do not allow for this
transition. In addition, we have assessed the impact of the cluster dynamical
state on the occurrence of the splashback feature. We exploited the extensive
multi-wavelength LoCuSS dataset to test a wide range of proxies for the cluster
formation history, finding the most significant dependence of the splashback
feature location and scale according to the presence or absence of X-ray
emitting galaxy groups in the cluster infall regions. In particular, we report
for the first time that clusters that do not show massive infalling groups
present the splashback feature at a smaller clustercentric radius $
r_{\rm{sp}}/r_{\rm{200,m}} = 1.158 \pm 0.071$ than clusters that are actively
accreting groups $r_{\rm{sp}}/r_{\rm{200,m}} = 1.291 \pm 0.062$. The difference
between these two sub-samples is significant at $4.2\sigma$, suggesting a
correlation between the properties of the cluster potential and its accretion
rate and merger history. Similarly, clusters that are classified as old and
dynamically inactive present stronger signatures of the splashback feature,
with respect to younger, more active clusters. We are directly observing how
fundamental dynamical properties of clusters reverberate across vastly
different physical scales.
