Merge and Strip II: Imprint of galaxy formation physics and viscosity on baryon-dominated dwarf galaxies

TL;DR

This study uses hydrodynamic simulations to explore how galaxy formation physics and viscosity influence the creation and stability of dwarf galaxies, including tidal dwarf galaxies, in cluster environments.

Contribution

It demonstrates that long-lived tidal dwarf galaxies can form across various viscosities with moderate stellar feedback, supporting their role in observed peculiar dwarf galaxies.

Findings

Long-lived TDGs form at all viscosities with moderate feedback.

Small gas clouds reach low drift velocities (~100 km/s).

Most TDGs exhibit stable star formation rates over several Gyr.

Abstract

Motivated by the discovery of peculiar dwarf galaxies inside galaxy clusters such as blue candidates (BCs), dark galaxies and ultra-diffuse galaxies (UDGs), we present hydrodynamic simulations of galaxy mergers in cluster environments. We vary the viscosity and stellar feedback prescriptions, realistically modelling possible conditions for hydrodynamic drag and fluid instabilities, as well as internal destabilization through stellar feedback-driven heating and gas loss. We find that long-lived tidal dwarf galaxies (TDGs) can form throughout all viscosity values applicable to galaxy clusters if stellar feedback is moderate. Our results expand on studies of cloud crushing simulations, investigating the entrainment problem in intracluster medium ambience. The smallest clouds have gas masses on the order of $M_\text{gas} \sim 10^7 \text{ M}_\odot$ and reach relatively low final drift velocities of $\sim 100 \text{ km/s}$. The lowest possible Reynolds number acting on this class of clouds is $Re \sim 1$ for full Spitzer viscosity. Almost all TDGs display elevated star formation rates of $0.01-0.1 \text{ M}_\odot / \text{yr}$, which are stable across several Gyr. Based on their matching properties, we support that BCs observed in the Virgo cluster are likely stripped TDGs. Similar features are also found in comparison with dark galaxies and baryon-dominated UDGs, implying that a subsample of these objects are also long-lived TDGs. This work provides robust evidence that stripping from galaxy mergers is a viable channel for the formation of stable cold gas clouds and dark matter-deficient galaxies observed in galaxy clusters.