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of the cluster centre were interpolated using all simulation snapshots between the time of the galaxy’s infall and z = 0, using a cubic interpolation between each pair of successive snapshots based on the halo positions and velocities deter- mined by SUBFIND . The results are shown for three different stellar mass ranges of the infalling galaxy. We see that only few stars are stripped from galaxies that never come close to the cluster centre. On the other hand, galaxies that closely approach the cluster centre are often substantially stripped, completely tidally disrupted, or merge with the BCG. This confirms the expectation that most of the tidal interactions that liberate intracluster stars happen close to the cluster centre and the BCG. 

## 4 SUMMARY AND CONCLUSIONS 

The intracluster light in clusters of galaxies represents an interesting and significant component of their total stellar mass. While the observational constraints on the ICL are still uncertain, some studies have reported intracluster star fractions of up to ∼ 50%. Even if the true fraction is sig- nificantly lower, it is therefore clear that the ICL can not be neglected in the baryon and stellar mass budgets of clus- ters. Furthermore, the radial profile of the ICL and the mass contained in it may pose interesting constraints on galaxy cluster formation models. Yet, comparatively little theoret- ical work has been carried out thus far on the formation of the ICL. In fact, most semi-analytic models of galaxy for- mation have hitherto ignored this component entirely. 

In this work we have therefore studied the origin of in- tracluster stars in a set of high-resolution hydrodynamical simulations of the formation of clusters of galaxies, embed- ded in their appropriate cosmological setting. Our sample of resimulations has been randomly drawn from the Mil- lennium simulation, with the only selection criterion being to provide a wide coverage of group and cluster masses, of roughly two orders of magnitude in halo mass. Thanks to the very high mass and force resolution of our resimulations, our simulations provide a powerful and representative sample of 

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the whole cluster population. Another very timely aspect of our simulations is that we not only account for hydro- dynamics, radiative cooling, heating by a UV background, star formation and supernovae feedback, but also incorpo- rate a state-of-the-art model for the growth of supermassive black holes and for feedback from AGN. Because we simu- lated each cluster both with and without AGN physics, this allows us to pinpoint the impact of AGN heating on the cluster galaxy populations, and in particular on the ICL. 

Our results clearly confirm the importance of AGN feedback in galaxy clusters. AGN lead to a reduction of the amount of stars in our clusters and groups by about one third, roughly independent of cluster mass. Especially the stellar masses and luminosities of BCGs are greatly re- duced by AGN feedback, and their stellar populations be- come much older. As a consequence, the BCGs are in much better agreement with observational constraints. Further- more, in poor clusters and groups, the total baryon fractions within r crit 500 become significantly lower when AGN heating is included. 

The primary focus of our analysis has been on the amount and the origin of the ICL component in our sim- ulated groups and clusters. In order to allow a meaningful comparison of our simulation results with observations of 

