Measuring the dynamical state of Planck SZ-selected clusters: X-ray peak
  - BCG offset
  We want to characterize the dynamical state of galaxy clusters detected with
the Sunyaev-Zeldovich (SZ) effect by Planck and compare them with the dynamical
state of clusters selected in X-rays survey. We analyzed a representative
subsample of the Planck SZ catalogue, containing the 132 clusters with the
highest signal to noise ratio and characterize their dynamical state using as
indicator the projected offset between the peak of the X-ray emission and the
position of the Brightest cluster galaxy. We study the distribution of our
indicator in our sample and compare it to its distribution in X-ray selected
samples (HIFLUGCS, MACS and REXCESS). The distributions are significantly
different and the fraction of relaxed objects is smaller in the Planck sample
($52 \pm 4 \%$) than in X-ray samples ($\simeq 74\%$) We interpret this result
as an indication of different selection effects affecting X-rays (e.g. "cool
core bias") and SZ surveys of galaxy clusters.
