Galaxy Cluster Mass Reconstruction Project: II. Quantifying scatter and
  bias using contrasting mock catalogues
  This article is the second in a series in which we perform an extensive
comparison of various galaxy-based cluster mass estimation techniques that
utilise the positions, velocities and colours of galaxies. Our aim is to
quantify the scatter, systematic bias and completeness of cluster masses
derived from a diverse set of 25 galaxy-based methods using two contrasting
mock galaxy catalogues based on a sophisticated halo occupation model and a
semi-analytic model. Analysing 968 clusters, we find a wide range in the RMS
errors in log M200c delivered by the different methods (0.18 to 1.08 dex, i.e.,
a factor of ~1.5 to 12), with abundance matching and richness methods providing
the best results, irrespective of the input model assumptions. In addition,
certain methods produce a significant number of catastrophic cases where the
mass is under- or over-estimated by a factor greater than 10. Given the steeply
falling high-mass end of the cluster mass function, we recommend that richness
or abundance matching-based methods are used in conjunction with these methods
as a sanity check for studies selecting high mass clusters. We see a stronger
correlation of the recovered to input number of galaxies for both catalogues in
comparison with the group/cluster mass, however, this does not guarantee that
the correct member galaxies are being selected. We do not observe significantly
higher scatter for either mock galaxy catalogues. Our results have implications
for cosmological analyses that utilise the masses, richnesses, or abundances of
clusters, which have different uncertainties when different methods are used.
