Below the iceberg: Extended low surface brightness structures with HST and Euclid

Deep imaging is the next frontier for galaxy evolution and cosmology. From the outer galactic discs and halos, to the remnants of their hierarchical formation, low surface brightness observations trace the limits of the intergalactic medium providing strong tests for the Lambda-CDM cosmological model. Nevertheless, pushing the surface brightness limits to such faint levels requires an increasing advance in image processing. Upcoming space observatories like NGRST or Euclid have the potential to become major cornerstones for the study of galactic formation and evolution, not only at high redshift, but also at the dim and extended envelopes of the objects in the Local Universe. In this contribution we present a set of techniques that make possible to reveal the large scale structures that surrounds the galaxies with the Hubble Space Telescope, and their application for the Euclid/VIS survey. Using specific techniques to minimise the systematic effects, structures can be detected down to ~31 mag arcsec⁻². We demonstrate these methods creating a new version of the WFC3/IR Hubble Ultra Deep Field (ABYSS HUDF), which improves the detection of extended halos that were invisible until now. The new mosaics reveal that some objects were nearly double the size than in the previously thought. This new methodology will be fundamental for future space missions if we want to exploit their capabilities to their true limit, providing unique datasets to study the local Universe and beyond