Tidally induced warps of spiral galaxies in IllustrisTNG

Warps are common features in both stellar and gaseous discs of nearby spiral galaxies with the latter usually easier to detect. Several theories have been proposed in the literature to explain their formation and prevalence, including tidal interactions with external galaxies. Observational correlations also suggest the importance of tides for warp formation. Here, we use the TNG100 run from the magnetohydrodynamical cosmological simulation suite IllustrisTNG to investigate the connection between interactions and the formation of gas warps. We find that in the sample of well-resolved gas-rich spiral galaxies (10¹⁰ ≲ M_*/M_⊙ ≲ 10¹¹ at z = 0) from the simulation TNG100-1, about 16 per cent possess the characteristic S-shaped warp. Around one-third of these objects have their warps induced by interactions with other galaxies. Half of these interactions end with the perturber absorbed by the host by z = 0. We find that warps induced by interactions survive on average for <1 Gyr, similarly to the remaining S-shaped warps. The angle between the orbital angular momentum of the perturber and the angular momentum of the host's disc that most likely leads to warp formation is around 45°. While our main goal is to investigate tidally induced warps, we find that during interactions in addition to tides, new gas that is accreted from infalling satellites also can contribute to warp formation.