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There is a huge amount of astrophysical events that remain barely studied due to the lack of large, deep surveys. This is the Universe at the lowest density of stars, largely unknown even though it promises to deliver transformational insights in our knowledge of the star formation in galaxies in the lowest mass regime, the hierarchical assembly of galaxies and clusters of galaxies, and the ultimate nature of dark matter. Deep space observations have expanded our knowledge of the properties of these faint features (e.g., HUDF, Frontier Fields) while at the same time allowing us to find unique objects. However, wide areas and larger samples are needed in order to map the full range of properties of these structures and, therefore, constrain our theoretical paradigm. Roman has the power to end this scarcity of sufficiently good quality data. In this talk, I will outline the tremendous discovery potential of Roman in the Low Surface Brightness Universe and give some examples of what might wait for the Roman eye. There is a huge amount of astrophysical events that remain barely studied due to the lack of large, deep surveys. This is the Universe at the lowest density of stars, largely unknown even though it promises to deliver transformational insights in our knowledge of the star formation in galaxies in the lowest mass regime, the hierarchical assembly of galaxies and clusters of galaxies, and the ultimate nature of dark matter. Deep space observations have expanded our knowledge of the properties of these faint features (e.g., HUDF, Frontier Fields) while at the same time allowing us to find unique objects. However, wide areas and larger samples are needed in order to map the full range of properties of these structures and, therefore, constrain our theoretical paradigm.

The vast majority of the mass in the Universe is expected to be in form of dark matter. Invisible as it is, it would be ideal to identify a luminous tracer that will mimic their spatial distribution. The distribution of stars within the galaxies is not a good tracer of the dark matter as they are originated in a dissipative process that locate most of the stars in the centre of the haloes. However, we expect that some stars whose spatial distribution results from the interactions of galaxies in the cluster follow the underlying dark matter distribution. These stars form the so called intracluster light (ICL). Here we compare the distribution of the dark matter mass in massive galaxy clusters (as traced by gravitational lensing models) with the distribution of ICL, using the exquisite data from the Hubble Frontier Fields. Using a shape matching measurement to assess the similarities, the Modified Hausdorff distance, we find an excellent agreement between the spatial distribution of the total mass and the intracluster light distribution. This gives us the first reliable luminous tracer of dark matter halos in galaxy clusters. Our finding opens the possibility to explore the dark matter distribution of galaxy clusters using only their low surface brightness light.

The intracluster light (ICL) is a unique tool to explore the assembly of clusters of galaxies over cosmic time. The ICL is thought to form by the stripping of satellite galaxies as they fall into the cluster. This means the amount of stellar debris floating in the gravitational potential of the cluster informs us about the violence and the timing of the processes that shaped the galaxies making up the cluster. In this talk, I will present the latest advances in our understanding of the ICL. Using the multiwavelength observations provided by the Hubble Frontier Fields, I have analysed the stellar populations of the ICL in 6 clusters at z~0.4, a particularly interesting time to explore the ICL as it is predicted to have formed since z~1. Our results suggest that the ICL of these massive (> 10^15 Msol) clusters is formed by the stripping of MW-like galaxies that have been accreted at z

Galaxy Clusters Across Cosmic Time : oral contribution