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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.