Survival of higher overdensity cold gas in a turbulent, multiphase medium

Abstract

Cold gas clouds embedded in a hot, turbulent medium are expected to be short-lived due to disruptive hydrodynamic instabilities. However, radiative cooling might allow such clouds to survive and grow. We present 3D \texttt{Athena++} simulations of clouds with a density contrast of $\chi =1000$, exploring turbulent Mach numbers $\mathcal{M}\in (0.25,0.75)$ and cloud radii chosen to span cooling-to-crushing ratios $\alpha \in [0.001,10]$. We find a shift in the survival boundary, with cloud survival occurring only when the cooling-to-cloud-crushing ratio ($t_{\text{cool,mix}}/t_{\text{cc}}$) $\lesssim 0.01$, which is lower than the expected boundary of $\sim 1$. This result shows that it is more difficult for higher over-density cold clouds to survive in a turbulent, hot medium, and suggests another `survival criterion'.