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

This is the authors' abstract. We don't add key points for this paper.

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 modeling 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 the intracluster medium ambience. The smallest clouds have gas masses on the order of M gas ∼ 10 7 M ⊙ and reach relatively low final drift velocities of ∼100 km/s. The lowest possible Reynolds number acting on this class of clouds is Re ∼ 1 for a full Spitzer viscosity. Almost all TDGs display elevated star formation rates of 0.01 − 0.1 M ⊙ /yr, which are stable across several gigayears. 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 evidence that stripping from galaxy mergers is a viable formation channel for a subgroup of dark-matter-deficient galaxies and stable cold gas clouds observed in galaxy clusters.