The orientation of planes of dwarf galaxies in the quasi-linear Universe

TL;DR

This study investigates the alignment of dwarf galaxy planes with the cosmic web's large-scale structure, extending previous work by analyzing more planes and using a more refined quasi-linear reconstruction.

Contribution

It extends prior analysis by including additional dwarf galaxy planes and employing a quasi-linear field reconstruction to better understand their orientations.

Findings

Previous alignment results are recovered.

Additional 5 planes show no tight alignment.

Plane normals are not randomly oriented.

Abstract

To date at least 10 highly flattened planes of dwarf galaxies are claimed to have been discovered in the Local Universe. The origin of these planes of galaxies remains unknown. One suggestion is that they are related to the large-scale structure of the cosmic web. A recent study found that the normal of a number of these dwarf galaxy planes are very closely aligned with the eigenvector of the shear tensor corresponding to the direction of greatest collapse obtained by reconstructing the full velocity field in the linear regime. Here we extend that work by both considering an additional 5 planes beyond the 5 examined previously and by examining the alignment with respect to the quasi-linear field, a more sophisticated reconstruction, which is a better approximation on smaller (quasi-linear) scales. Our analysis recovers the previous result while not finding a significantly tight alignment with the additional 5 planes. However, the additional 5 planes normals also do not appear to be randomly oriented. We conclude that this could either be due to the normals of the new planes being poorly defined and described; the quasi-linear field at those locations being poorly constrained; or different formation mechanisms for the orientation of planes of dwarf galaxies.