The next-generation of wide-field galaxy surveys, known as Stage IV experiments, aims to investigate the "dark sector" by mapping a significant fraction of the observable Universe at unprecedented depth. In doing so, these surveys will also contribute to transform our understanding of galaxy formation and evolution. Their vast statistical power is however limited by systematic effects that dominate over the statistical uncertainties of the measurements, with redshift calibration being one of the dominant observational systematics for Stage IV large scale structure cosmology. In this talk I will describe the two complementary approaches I am leading to tackle the redshift calibration problem for next generation surveys. On one side, I will introduce the 4MOST Complete Calibration of the Colour Redshift Relation survey, which has recently finished its survey verification phase, and is designed to obtain more than 300k spectroscopic redshifts for a sample of galaxies that cover the colour SOM representative of the manifold spanned by Euclid and Rubin-LSST. Complementary to this, I will introduce my approach to the forward-modelling of photometric and spectroscopic galaxy surveys, a method that bridges cosmology with galaxy evolution, that consists of generating physically motivated galaxy populations, mapping them to multi-band observables, and producing realistic mock survey images and spectra that can be passed through the same detection, measurement, and selection steps as the data. I will discuss the past (Tortorelli+18,20,21) and on-going efforts (Tortorelli+24, Tortorelli+25) in forward-modelling galaxy surveys, from the modelling of the galaxy population (GalSBI-SPS) to the simulation of images (UFig) and fiber-based spectra (USpec), targeting 4MOST and DESI spectra, but extendable to other fiber-based spectrographs (e.g. PFS). The model is currently being constrained against HSC Deep observations, whose depth and blending regime make them a valuable precursor of Stage IV surveys, and used to measure the Galaxy Stellar Mass Function in these fields. This approach allows us to use a physically grounded population model to reproduce the observed colour, magnitude, and size distributions precisely in the regime where conventional redshift calibration is most challenging, thus obtaining redshift distribution with the precision required for Stage IV cosmological analyses.

Evolved stars are the primary engines of galactic chemical enrichment, yet the physical mechanisms governing their intense mass loss remain a major challenge for stellar evolution models. While mass loss is traditionally treated as a spherically symmetric process, the high frequency of binary systems suggests that gravitational interactions with a companion are a dominant force in shaping stellar outflows.

In this talk, I present a high-resolution observational study of the post-Red Supergiant (post-RSG) binary system AFGL 4106. Using the extreme adaptive optics and high-contrast imaging capabilities of VLT/SPHERE, we have successfully resolved the binary components and mapped their immediate circumstellar environment in unprecedented detail.

These observations (Tomassini et al. 2026) reveal a complex interplay between the binary pair and the surrounding material, providing a unique window into how companions steer mass loss during the final stages of stellar evolution. By characterising the morphology of the dusty structures surrounding AFGL 4106, we provide crucial empirical constraints for 3D hydrodynamic models of binary interactions in evolved systems.

Probing the composition of exoplanet atmospheres reveals the physical processes at play and provides insights into their interior and formation history. Atmospheric temperatures are key in shaping these atmospheres and setting molecular abundances. However, warm exoplanets (Teq < 1000 K) are not well understood. JWST opened a new window into these atmospheres thanks to its broad coverage from red to mid-infrared wavelengths and unprecedented sensitivity. Carbon- and sulphur-bearing species are now detected with high significance and their abundances can be measured. In this talk, I will give new insights on the atmospheres of transiting gas giant exoplanets focusing on the warm Neptune WASP-107b, the warm sub-Saturn HAT-P-12b, and the hot Jupiter WASP-43b that has a warm nightside. These studies highlight the importance of processes that alter thermochemical equilibrium and the role of the atmospheric temperature, provide clues on the presence and composition of clouds, but also leaves unanswered questions. I will also present other projects that I conduct with JWST, from the calibration of the MIRI instrument to the search for unknown asteroids.