Numerical simulations of starbursts triggered by tidal disruption in clusters: searching for observational signatures

ABSTRACT Tidal interactions are involved in the stellar stripping of galaxies, one of the main scenarios invoked to explain the origin of intracluster light (ICL), and fully compressive tides can also trigger starbursts in those same galaxies. Detecting traces of tidally induced starbursts within the ICL would thus provide strong support for the stellar stripping scenario. To investigate this, we performed 36 simulations of isolated and tidally disrupted galaxies. We find the contribution of starburst stars to the ICL to be negligible, these stars remaining instead in the centre of the galactic remnant following the tidal interaction. Starbursts are observed in 60 per cent of simulations with tides, typically occurring as the galaxy reaches pericentre. In cases involving strong tidal forces, galaxies with an internal ring experience its asymmetric collapse, leading to its fragmentation into multiple star-forming clumps. The subsequent merging of these clumps triggers a second starburst and produces a substantial population of counter-rotating stars, leaving a transient signature in the stellar tangential velocity distribution, observable as a secondary peak to the left of the primary peak. Most interestingly, starbursts leave a distinct chemical signature: remnants that experienced a starburst exhibit lower [O/Fe] values in their central regions (within a 0.5 kpc radius) compared to isolated galaxies of equal stellar mass, with a mean difference of 0.201 dex.