Momentum and energy injection by a wind-blown bubble into an inhomogeneous interstellar medium

TL;DR

This paper studies how embedded clouds in an inhomogeneous interstellar medium affect wind-blown bubbles, revealing that mass-loading influences their size, energy, and momentum, making them more energy-conserving than previously thought.

Contribution

It introduces a 1D hydrodynamical model for mass-loading effects on wind-blown bubbles in inhomogeneous media, highlighting their impact on bubble evolution and energetics.

Findings

Mass-loading increases bubble density and modifies temperature distribution.

Mass-loaded bubbles are smaller with less energy and momentum.

Despite mass-loading, bubbles can still perform significant work on surrounding gas.

Abstract

We investigate the effect of mass-loading from embedded clouds on the evolution of wind-blown bubbles. We use 1D hydrodynamical calculations and assume that the clouds are numerous enough that they can be treated in the continuous limit, and that rapid mixing occurs so that the injected mass quickly merges with the global flow. The destruction of embedded clouds adds mass into the bubble, increasing its density. Mass-loading increases the temperature of the unshocked stellar wind due to the frictional drag, and reduces the temperature of the hot shocked gas as the available thermal energy is shared between more particles. Mass-loading may increase or decrease the volume-averaged bubble pressure. Mass-loaded bubbles are smaller, have less retained energy and lower radial momentum, but in all cases examined are still able to do significant $PdV$ work on the swept-up gas. In this latter respect, the bubbles more closely resemble energy-conserving bubbles than the momentum-conserving-like behaviour of ``quenched'' bubbles.