The global warming of group satellite galaxies

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.