Environment-based selection effects of Planck clusters
  We investigate whether the large scale structure environment of galaxy
clusters imprints a selection bias on Sunyaev Zel'dovich (SZ) catalogs. Such a
selection effect might be caused by line of sight (LoS) structures that add to
the SZ signal or contain point sources that disturb the signal extraction in
the SZ survey. We use the Planck PSZ1 union catalog (Planck Collab- oration et
al. 2013a) in the SDSS region as our sample of SZ selected clusters. We
calculate the angular two-point correlation function (2pcf) for physically
correlated, foreground and background structure in the RedMaPPer SDSS DR8
catalog with respect to each cluster. We compare our results with an optically
selected comparison cluster sample and with theoretical predictions. In
contrast to the hypothesis of no environment-based selection, we find a mean
2pcf for background structures of -0.049 on scales of $\lesssim 40'$,
significantly non-zero at $\sim 4 \sigma$, which means that Planck clusters are
more likely to be detected in regions of low background density. We hypothesize
this effect arises either from background estimation in the SZ survey or from
radio sources in the background. We estimate the defect in SZ signal caused by
this effect to be negligibly small, of the order of $\sim 10^{-4}$ of the
signal of a typical Planck detection. Analogously, there are no implications on
X-ray mass measurements. However, the environ- mental dependence has important
consequences for weak lensing follow up of Planck galaxy clusters: we predict
that projection effects account for half of the mass contained within a 15'
radius of Planck galaxy clusters. We did not detect a background underdensity
of CMASS LRGs, which also leaves a spatially varying redshift dependence of the
Planck SZ selection function as a possible cause for our findings.
