Environmental effects on galaxy evolution. II: quantifying the tidal
  features in NIR-images of the cluster Abell 85
  This work is part of a series of papers devoted to investigate the evolution
of cluster galaxies during their infall. In the present article we imaged in
NIR a selected sample of galaxies through- out the massive cluster Abell 85 (z
= 0.055). We obtained (JHK) photometry for 68 objects, reaching 1 mag/arcsec^2
deeper than 2MASS. We use these images to unveil asymmetries in the outskirts
of a sample of bright galaxies and develop a new asymmetry index, alpha_An,
which allows to quantify the degree of disruption by the relative area occupied
by the tidal features on the plane of the sky. We measure the asymmetries for a
subsample of 41 large area objects finding clear asymmetries in ten galaxies,
most of them being in groups and pairs projected at different clustercentric
distances, some of them located beyond R500 . Combining information on the
Hi-gas content of blue galaxies and the distribution of sub-structures across
Abell 85, with the present NIR asymmetry analysis, we obtain a very powerful
tool to confirm that tidal mechanisms are indeed present and are currently
affecting a fraction of galaxies in Abell 85. However, when comparing our deep
NIR images with UV-blue images of two very disrupted (jellyfish) galaxies in
this cluster, we discard the presence of tidal 1 interactions down to our
detection limit. Our results suggest that ram-pressure stripping is at the
origin of such spectacular disruptions. We conclude that across a complex
cluster like Abell 85, environment mechanisms, both gravitational and
hydrodynamical, are playing an active role in driving galaxy evolution.
