Keynote Lecture: Galactic and Extragalactic Bubbles

TL;DR

This paper reviews the current understanding of galactic and extragalactic bubbles, emphasizing observations, analytical models, and high-resolution simulations to explain their morphology and properties, especially focusing on the Local Bubble.

Contribution

It presents new high-resolution 3D simulations of the Local Bubble and Loop I, demonstrating their formation from supernova explosions in an inhomogeneous medium, aligning with recent observational data.

Findings

The Local Bubble likely resulted from about 20 supernovae.

The LB age is estimated at approximately 14.7 million years.

Simulations successfully reproduce observed OVI absorption line data.

Abstract

The observational and theoretical state of Galactic and extragalactic bubbles are reviewed. Observations of superbubbles are discussed, with some emphasis on nearby bubbles such as the Local Bubble (LB) and the Loop I superbubble (LI). Analytical bubble theory is revisited, and similarity solutions, including the time-dependent energy input by supernova explosions according to a Galactic initial mass function (IMF), are studied. Since the agreement with observations is not convincing in case of the LB, we present high resolution 3D AMR simulations of the LB and LI in an inhomogeneous background medium. It is demonstrated that both the morphology and recently published FUSE data on OVI absorption line column densities can be well understood, if the LB is the result of about 20 supernova explosions from a moving group, and the LB age is about 14.7 Myrs.