Abstract:
We use an information theoretic framework to analyse data from the Galaxy Zoo 2 project and study if there are any statistically
significant correlations between the presence of bars in spiral galaxies and their environment. We measure the mutual information
between the barredness of galaxies and their environments in a volume limited sample (Mr ≤ −21) and compare it with the same
in data sets where (i) the bar/unbar classifications are randomized and (ii) the spatial distribution of galaxies are shuffled on
different length scales. We assess the statistical significance of the differences in the mutual information using a t-test and find
that both randomization of morphological classifications and shuffling of spatial distribution do not alter the mutual information
in a statistically significant way. The non-zero mutual information between the barredness and environment arises due to the
finite and discrete nature of the data set that can be entirely explained by mock Poisson distributions. We also separately
compare the cumulative distribution functions of the barred and unbarred galaxies as a function of their local density. Using a
Kolmogorov–Smirnov test, we find that the null hypothesis cannot be rejected even at 75 per cent confidence level. Our analysis
indicates that environments do not play a significant role in the formation of a bar, which is largely determined by the internal
processes of the host galaxy
