Master thesis defense by Athanasios Anastasiou

Abstract:

Galaxy formation and evolution is a field driven forward by large multiwavelength surveys. Through the acquired data, we managed to improve our models of galaxy evolution. However, there are pieces of observational evidence still in tension with theoretical models. One of these is the observation of massive quenched galaxies being at place already at 2 < z < 3, which is in contrast with the hierarchical paradigm of dark halo formation. In this thesis I will present the new COSMOS 2020 catalog, a deep panchromatic survey with updated imaging and spectroscopic data over
2 deg2 of sky. New deeper data in UV, optical and near-infrared are added from Canada-France-Hawaii Telescope, Subaru/Hyper Supreme Cam DR2, UVISTA DR4 alongside all legacy surveys conducted on COSMOS field with Spitzer Space Telescope. A novelty introduced in the data release by the COSMOS collaboration is the implementation of two different photometric extraction methods to make two versions of the same catalog: one with traditional aperture photometry (SExtractor) and other with forced model photometry model (Farmer). The new catalog is reaching a limiting depth of Ks = 25.2 mag (3", 3s) which is 0.5 mag deeper than the previous version of the catalog (COSMOS 2015). Multiple number counts comparisons are presented here, to show the agreement with the literature as well as the progress in terms of depth (although I found that Farmer is missing i-bright sources). The derived photometric redshifts are compared with a large spectroscopic sample from different surveys. Catastrophic outliers constitute only 3.1% of the sample while the photometric precision is s = 0.011. A separation of stars and galaxies is done based on the basis of the gzKs diagram and the c2 comparison between galactic and stellar template fit. With the help of NUVrJ diagram and the SFR-M⇤ correlation formula I selected quiescent galaxy candidates. The final sample is cross-matched with confirmed quiescent galaxies from the literature. A spectroscopic follow-up of the candidates in the future can help investigate the open questions of mass assembly and star formation quenching.

Supervisors: Georgios Magdis & Iary Davidzon, Niels Bohr Insitute, DAWN

Censor: Maximillian Stritzinger (Aarhus University)