Numerical effects on the stripping of dark matter and stars in IllustrisTNG galaxy groups and clusters

ABSTRACT The stellar haloes and intracluster light around galaxies are crucial test beds for dark matter (DM) physics and galaxy formation models. We consider the role that the numerical resolution plays in the modelling of these systems by studying the stripping of satellites in the IllustrisTNG cosmological simulations. We focus on host haloes of total halo mass $M_{\rm 200c}=10^{12-15}{\, \rm M_\odot }$ and satellites of stellar mass $>10^{7}\, {\, \rm M_\odot }$, and compare stellar halo/satellite properties across nine IllustrisTNG runs with baryonic particle mass resolution between $8.5\times 10^4$ and $7\times 10^8\, {\, \rm M_\odot }$, using a Lagrangian-region technique to identify counterpart satellites across different resolution simulations of the same volume. We publish the corresponding catalogues alongside this paper. We demonstrate that the stripping of DM from satellites that orbit in group- and cluster-mass hosts is largely independent of resolution at least until 90 per cent of their initial mass at infall has been stripped. We do not find evidence for spurious disruption of galaxies due to insufficient resolution for the satellite masses we consider. By contrast, the stripping of stellar mass is strongly resolution-dependent: each factor of eight improvement in particle stellar mass typically adds 2 Gyr to the stripping time. Improved numerical resolution within the IllustrisTNG model generally results in more compact satellites with larger stellar masses, which in turn generate more centrally concentrated stellar haloes and intracluster mass profiles. However, the concomitant increase in stellar mass with increased resolution of both satellites and hosts may still be the cause for the overprediction of the stellar halo mass at large host radii relative to observations seen in some previous studies.