Regular chains of star formation regions in spiral arms and rings of disk galaxies

TL;DR

This paper reviews recent observations showing that regular chains of star-forming regions in spiral arms and rings of disk galaxies are common, with a characteristic scale of 350-500 pc, challenging existing theoretical models.

Contribution

It presents new observational evidence that the spatial regularity scale of star formation regions is smaller than predicted by current theoretical models.

Findings

Regular chains of star-forming regions are common in spiral arms and rings.

The characteristic regularity scale is 350-500 pc, smaller than theoretical predictions.

Spatial regularity is observed across multiple galaxy types.

Abstract

The regularity in the distribution of young stellar groups along the spiral arms of galaxies, first discovered by Bruce and Debra Elmegreen in 1983, was considered a rather rare phenomenon. However, recent studies of the spatial regularities in the distribution of the young stellar populations along the arms of the spiral galaxies NGC 628, NGC 895, NGC 4321, NGC 5474, NGC 6946, as well as along the rings of the spiral galaxy NGC 6217 and the lenticular galaxy NGC 4324, have revealed that this spatial (quasi) regularity and/or the presence of regular chains of star-forming regions is a fairly common phenomenon. Across all galaxies, the characteristic regularity scale is 350-500 pc or a multiple thereof. It should be noted that theoretical models predict an instability scale of a stellar-gas disk on the order of a few kpc, which is several times larger than what has been observed. The paper is partly based on the report presented at the Modern Stellar Astronomy 2022 Conference held at the Caucasian Mountain Observatory of the Sternberg Astronomical Institute, Moscow State University, on November 8-10, 2022.