Galaxy Zoo: A correlation between coherence of galaxy spin chirality and star formation efficiency

TL;DR

This study finds a significant correlation between galaxy spin alignment and early star formation activity, supporting hierarchical tidal-torque theory and revealing environmental influences on galaxy evolution.

Contribution

It demonstrates a novel link between galaxy spin coherence and star formation history, using cross-correlation of SDSS data and Galaxy Zoo classifications.

Findings

Galaxies with early star formation show coherent spin alignment over ~10 Mpc/h.

Weaker alignment observed in galaxies with recent star formation.

Alignment significance exceeds 5 sigma, with no correlation to other stellar properties.

Abstract

We report on the finding of a correlation between galaxies' past star formation activity and the degree to which neighbouring galaxies rotation axes are aligned. This is obtained by cross-correlating star formation histories, derived with MOPED, and spin direction (chirality), as determined by the Galaxy Zoo project, for a sample of SDSS galaxies. Our findings suggest that spiral galaxies which formed the majority of their stars early (z > 2) tend to display coherent rotation over scales of ~10 Mpc/h. The correlation is weaker for galaxies with significant recent star formation. We find evidence for this alignment at more than the 5-sigma level, but no correlation with other galaxy stellar properties. This finding can be explained within the context of hierarchical tidal-torque theory if the SDSS galaxies harboring the majority of the old stellar population where formed in the past, in the same filament and at about the same time. Galaxies with significant recent star formation instead are in the field, thus influenced by the general tidal field that will align them in random directions or had a recent merger which would promote star formation, but deviate the spin direction.