Are there more galaxies than we see around high-z quasars? Tommaso Zana, Stefano Carniani, David Prelogović, Fabio Vito, Viola Allevato, Andrea Ferrara, Simona Gallerani and Eleonora Parlanti A&A, 679 (2023) A77 Published online: 10 November 2023 DOI: 10.1051/0004-6361/202347172