The formation and evolution of galaxies depends on the interaction between dark matter, gas, and stars. While dark matter aggregates into larger and larger structures (halos) through processes of gravitational interaction and mergers, the evolution of baryonic matter depends both on the collapse within the potential wells created by the dark matter, and on complex physical processes that allow star formation starting from the dissipative collapse of the primordial gas.
These processes are thus influenced by several factors, including the environment in which galaxies reside.
In the past years the astronomical community made progress in the comprehension of phenomena that drive galaxy evolution, thanks to several extragalactic spectroscopic surveys (for example, VVDS, zCOSMOS, VIPERS, VUDS, VANDELS…), to which several researchers in OAS vastly contributed. For instance, thanks to the redshift measurement of large galaxy samples it is possible to characterise the large-scale structure on which galaxies are embedded, i.e. the 3-dimensional reconstruction of galaxy distribution. Moreover, the estimation of typical galaxy properties (luminosity, colours, stellar mass, morphology, star formation rate, age, metallicity…) based on photometric and spectroscopic data allowed to determine how galaxies evolve as a function of redshift and as a function of their position in the so called cosmic web.
Galaxy clusters, that correspond to the highest peaks in the cosmological density field, can be used both as tracers of the large-scale structure, and thus as sensitive probes of the cosmological model, and as crucial loci where to study how galaxy evolution depends on the environment in which galaxies form. In this context, it is crucial not only to identify clusters and their member galaxies, but also to detect the progenitors of galaxy clusters (the so called proto-clusters) at higher redshift, to identify the epoch when environmental effects became efficient in shaping galaxy evolution.
In the near future, surveys based for instance on the satellite Euclid or the MOONS spectrograph, in which OAS researches have major roles, will study redshift and wavelength regimes currently not yet explored, and will allow the astronomical community to use richer galaxy samples.
The extragalactic team in OAS is also involved in the preparation of numerical simulations which are needed for the optimization of future surveys. Such simulations are becoming more and more important in this field, as they allow both to give forecasts on the measurements that we expect to obtain from the future observations, and to improve the tools for data analysis.
Last but not least, the multi-wavelength galaxy characterization carried on in OAS comprises also the study of the cold component of dust and interstellar medium.