Straight segments in the galactic discs

TL;DR

This study investigates straight segments in galactic discs using N-body simulations, showing they form due to gravitational responses to overdensities, aligning with observational data and differing from gas instability explanations.

Contribution

The paper demonstrates that straight segments in galactic discs form from stellar dynamics responding to overdensities, not gas instabilities, providing a new understanding of their origin.

Findings

Properties match observational data

Segments form from stellar gravitational response

Kinematics support the overdensity hypothesis

Abstract

We study the properties of the straight segments forming in N-body simulations of the galactic discs. The properties of these features are consistent with the observational ones summarized by Chernin at al. (2001). Unlike some previous suggestions to explain the straight segments as gas dynamical instabilities, they form in our models in the stellar system. We suggest that the straight segments are forming as a response of the rotating disc to a gravity of the regions of enhanced density (overdensities) corotating with the disc. The kinematics of stars near the prominent overdensities is consistent with this hypothesis.