VGS31b: a highly inclined ring along a filament in a void. Implication
  for the cold accretion
  VGS31b is a highly-inclined ring galaxy found along a filament in a void
(Kreckel et al. 2012). Detailed photometry, by using u, g, r, i, z SDSS images,
has shown that the overall morphology of VGS31b is very tricky, due to (i) the
presence of a highly inclined (72 deg) ring-like structure, which reaches the
galaxy center tracing a "spiral-like" pattern, (ii) a one sided tail towards
North-East and (iii) a bar in the central regions (Beygu et al. 2013). Such
structure is reasonably the result of a "second event" in the evolution history
of this galaxy, which could be a gravitational interaction with a companion
galaxy or with the environment.
  The main aim of the present work is to address the most reliable formation
scenario for this object, by comparing the observed properties, i.e. structure,
baryonic mass, kinematics and chemical abundances, with the theoretical
predictions. In particular, we have used archival spectroscopic data, to derive
the metallicity in the ring: we found a very low, sub-solar average value of Z
= 0.3 Zsun, comparable with other polar ring/disk galaxies, but lower than
those measured for ordinary spirals of similar luminosity. The study of the
chemical abundances in polar ring/disk galaxies and related objects has
received an increasing attention in recent years, since it has revealed to be a
key-parameter to disentangle among the formation scenarios suggested for this
class of objects: major merging, tidal accretion or cold accretion. In the
present work we check the cold accretion of gas through a "cosmic filament" as
a possible scenario for the formation of the ring-like structure in VGS31b.
