How much a galaxy knows about its large-scale environment?: An information theoretic perspective

TL;DR

This paper uses information theory to quantify how large-scale environments influence galaxy morphology, revealing persistent interactions across scales up to about 30 Mpc/h.

Contribution

It introduces an information theoretic framework to analyze the impact of large-scale environment on galaxy properties, applying it to Galaxy Zoo data for the first time.

Findings

Mutual information between galaxy morphology and environment is non-zero and persists across scales.

Interaction information reveals synergic effects between different environmental scales.

Environmental influence on galaxy morphology extends up to approximately 30 Mpc/h.

Abstract

The small-scale environment characterized by the local density is known to play a crucial role in deciding the galaxy properties but the role of large-scale environment on galaxy formation and evolution still remain a less clear issue. We propose an information theoretic framework to investigate the influence of large-scale environment on galaxy properties and apply it to the data from the Galaxy Zoo project which provides the visual morphological classifications of $\sim 1$ million galaxies from the Sloan Digital Sky Survey. We find a non-zero mutual information between morphology and environment which decreases with increasing length scales but persists throughout the entire length scales probed. We estimate the conditional mutual information and the interaction information between morphology and environment by conditioning the environment on different length scales and find a synergic interaction between them which operates upto at least a length scales of $ \sim 30 \, h^{-1}\, {\rm Mpc}$. Our analysis indicates that these interactions largely arise due to the mutual information shared between the environments on different length scales.