The effect of clouds on the dynamical and chemical evolution of gas-rich dwarf galaxies

TL;DR

This study investigates how clouds influence the dynamical and chemical evolution of gas-rich dwarf galaxies, showing that clouds can delay outflows, retain gas, and dilute metallicity, with effects depending on cloud creation scenarios.

Contribution

It introduces models with clouds at different stages, revealing their role in cooling, delaying outflows, and affecting metallicity in dwarf galaxy evolution.

Findings

Clouds act as cooling agents, reducing internal energy by 20-40%.

Clouds delay large-scale outflows, helping gas retention.

Infalling clouds can create holes, allowing metal venting and diluting metallicity.

Abstract

We study the effects of clouds on the dynamical and chemical evolution of gas-rich dwarf galaxies, in particular focusing on two model galaxies similar to IZw18 and NGC1569. We consider both scenarios, clouds put at the beginning of the simulation and continuously created infalling ones. Due to dynamical processes and thermal evaporation, the clouds survive only a few tens of Myr, but during this time they act as an additional cooling agent and the internal energy of cloudy models is typically reduced by 20 - 40% in comparison with models without clouds. The clouds delay the development of large-scale outflows, therefore helping to retain a larger amount of gas inside the galaxy. However, especially in models with continuous creation of infalling clouds, their bullet effect can pierce the expanding supershell and create holes through which the superbubble can vent freshly produced metals. Moreover, assuming a pristine chemical composition for the clouds, their interaction with the superbubble dilutes the gas, reducing the metallicity (by up to ~ 0.4 dex) with respect to the one attained by diffuse models.