In the first year of operations, JWST has revolutionized extragalactic astronomy, unveiling an unforeseen rapid evolution of structures in the early Universe, at odds with most theoretical predictions. In particular, a population of massive, passively evolving galaxies already in place at redshift >3 has been found and spectroscopically confirmed, strengthening the results of early studies conducted with HST data before the launch of Webb. I will summarise the state of the art and discuss photometric selection criteria based on SED fitting techniques to find robust candidates and quantify the number density of these objects, exploiting the recently published ASTRODEEP-JWST catalogs on six deep fields for a total area of ~580 sq.arcmin. Passive candidates are found up to redshift ~7-8; I will show number density estimates for 3<z<5, comparing them to theoretical predictions. The results highlight the tensions of the observed properties of the early Universe with the theoretical predictions of structure formation of the LCDM cosmological model.
Mauro D'Onofrio
