The Galactic Spatial Distribution of OB Associations and Their Surrounding Supernova-Generated Superbubble

TL;DR

This paper models the three-dimensional spatial distribution of OB associations and superbubbles in the Galaxy, using emission data to improve understanding of cosmic-ray propagation.

Contribution

It introduces a new 3D spatial model of massive star distribution based on H II envelope emissions, emphasizing spiral arm contributions.

Findings

Superbubbles are mainly located in spiral arms.

The model improves understanding of cosmic-ray source distribution.

OB associations significantly influence Galactic superbubble distribution.

Abstract

Core collapse supernovae of massive (> 8 Mo) stars are formed primarily in OB associations and help blow giant superbubbles, where their collective shocks accelerate most of the Galactic cosmic rays. The spatial distribution of these stars is thus important to our understanding of the propagation of the observed cosmic rays. In order to better model the Galactic cosmic-ray distribution and propagation, we construct s three-dimensional spatial model of the massive star distribution based primarily on the emission of the H II envelopes surrounding the giant superbubbles which are maintaned by the ionizing radiation of the embedded O stars. The Galactic longitudinal distribution of the 205 micron N II rsdistion emitted by these H II envelopes is used to infer the spatial distribution of the superbubbles. We find that the Galactic superbubble distribution is dominated by the contribution of massive star clusters residing in the spiral arms.