The role of the cosmic web in the scatter of the galaxy stellar mass -
  gas metallicity relation
  Understanding the relationship between the cosmic web and the gas content of
galaxies is a key step towards understanding galaxy evolution. However, the
impact of the cosmic web on the growth of galaxies and dark matter halos is not
yet properly understood. We report a detection of the effect of the cosmic web
on the galaxy stellar mass - gas phase metallicity relation of low redshift
star-forming galaxies, using SDSS data. The proximity of a galaxy to a node,
independently of stellar mass and overdensity, influences its gas-phase
metallicity, with galaxies closer to nodes displaying higher chemical
enrichment than those further away. We find a similar but significantly weaker
effect with respect to filaments. We supplement our observational analysis with
a study of the cosmological hydrodynamical simulation IllustrisTNG (TNG300),
finding qualitative agreement with our results. Using IllustrisTNG, our results
can be explained by both halo assembly bias and gas supply combining in nodes
in a way that significantly modulates the metallicity of the gas, contributing
to the scatter of this fundamental relation in galaxy evolution.
