How Significant is Radiation Pressure in the Dynamics of the Gas Around Young Stellar Clusters?

TL;DR

This paper evaluates the role of radiation pressure in young stellar cluster environments, concluding it is only significant early on and often overshadowed by wind-driven dynamics, with implications for interpreting X-ray observations.

Contribution

It provides a detailed analysis of the conditions under which radiation pressure influences gas dynamics around young stellar clusters, emphasizing the importance of cluster evolution and environment.

Findings

Radiation pressure impacts are limited to early stages of bubble evolution.

Wind-driven shells dominate after approximately 3 million years.

Thermal pressure profiles help distinguish between energy and momentum-driven regimes.

Abstract

The impact of radiation pressure on the dynamics of the gas in the vicinity of young stellar clusters is thoroughly discussed. The radiation over the thermal/ram pressure ratio time evolution is calculated explicitely and the crucial role of the cluster mechanical power and of the strong time evolution of the ionizing photon flux and of the bolometric luminosity of the exciting cluster is stressed. It is shown that radiation has only a narrow window of opportunity to dominate the wind-driven shell dynamics. This may occur only at early stages of the bubble evolution and if the shell expands into a dusty and/or a very dense proto-cluster medium. The impact of radiation pressure on the wind-driven shell becomes always negligible after about 3 Myr. Finally, the wind-driven model results allow one to compare the model predictions with the distribution of thermal pressure derived from X-ray observations. The shape of the thermal pressure profile allows then to distinguish between the energy and the momentum dominated regimes of expansion and thus conclude whether radiative losses of energy or the leakage of hot gas from the bubble interior have been significant during the bubble evolution.