Green valley galaxies in the cosmic web: internal versus environmental
  quenching
  We analyze the SDSS data to classify the galaxies based on their colour using
a fuzzy set-theoretic method and quantify their environments using the local
dimension. We find that the fraction of the green galaxies does not depend on
the environment and $10\%-20\%$ of the galaxies at each environment are in the
green valley depending on the stellar mass range chosen. Approximately $10\%$
of the green galaxies at each environment host an AGN. Combining data from the
Galaxy Zoo, we find that $\sim 95\%$ of the green galaxies are spirals and
$\sim 5\%$ are ellipticals at each environment. Only $\sim 8\%$ of green
galaxies exhibit signs of interactions and mergers, $\sim 1\%$ have dominant
bulge, and $\sim 6\%$ host a bar. We show that the stellar mass distributions
for the red and green galaxies are quite similar at each environment. Our
analysis suggests that the majority of the green galaxies must curtail their
star formation using physical mechanism(s) other than interactions, mergers,
and those driven by bulge, bar and AGN activity. We speculate that these are
the massive galaxies that have grown only via smooth accretion and suppressed
the star formation primarily through mass driven quenching. Using a
Kolmogorov-Smirnov test, we do not find any statistically significant
difference between the properties of green galaxies in different environments.
We conclude that the environmental factors play a minor role and the internal
processes play the dominant role in quenching star formation in the green
valley galaxies.
