Spin alignments of spiral galaxies within the large-scale structure from SDSS DR7

TL;DR

This study examines how spiral galaxy spins align with large-scale cosmic structures using SDSS DR7 data, revealing weak tendencies and environmental dependencies that support models of galaxy-halo angular momentum correlation.

Contribution

It provides the first observational evidence of spiral galaxy spin alignments with large-scale tidal fields, especially in cluster environments, linking galaxy disks to dark matter halo inner regions.

Findings

Weak alignment of galaxy spins with tidal field axes.

Strongest alignment observed in cluster environments.

Supports the idea that galaxy disks trace inner halo angular momentum.

Abstract

Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and Galaxy Zoo 2 (GZ2), we investigate the alignment of spin axes of spiral galaxies with their surrounding large scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes of only have weak tendency to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a \cluster environment where all the three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.