The global warming of group satellite galaxies

TL;DR

This study uses simulations to explore how tidal interactions influence the angular momentum and shape of satellite galaxies, predicting their evolution in group environments.

Contribution

It demonstrates that satellite galaxies remain fast rotators since infall and explains the role of bar/spiral cycles in their kinematic evolution, matching observations.

Findings

Satellites stay intrinsically fast-rotating since infall at z=2

Misidentifications of slow rotators often due to bar/spiral cycles

Simulated distribution matches observational data at low redshift

Abstract

Recent studies adopting $\lambda_{\rm Re}$, a proxy for specific angular momentum, have highlighted how early-type galaxies (ETGs) are composed of two kinematic classes for which distinct formation mechanisms can be inferred. With upcoming surveys expected to obtain $\lambda_{\rm Re}$ from a broad range of environments (e.g. SAMI, MaNGA), we investigate in this numerical study how the $\lambda_{\rm Re}$-$\epsilon_{\rm e}$ distribution of fast-rotating dwarf satellite galaxies reflects their evolutionary state. By combining N-body/SPH simulations of progenitor disc galaxies (stellar mass $\simeq$10$^{\rm 9}$ M$_{\odot}$), their cosmologically-motivated sub-halo infall history and a characteristic group orbit/potential, we demonstrate the evolution of a satellite ETG population driven by tidal interactions (e.g. harassment). As a general result, these satellites remain intrinsically fast-rotating oblate stellar systems since their infall as early as $z=2$; mis-identifications as slow rotators often arise due to a bar/spiral lifecycle which plays an integral role in their evolution. Despite the idealistic nature of its construction, our mock $\lambda_{\rm Re}$-$\epsilon_{\rm e}$ distribution at $z<0.1$ reproduces its observational counterpart from the ATLAS$^{\rm 3D}$/SAURON projects. We predict therefore how the observed $\lambda_{\rm Re}$-$\epsilon_{\rm e}$ distribution of a group evolves according to these ensemble tidal interactions.