RSN1: Finding clusters of galaxies in the Euclid spectroscopic survey

Dottorato - PhD thesis

Area Tematica: RSN 1 - Galassie e cosmologia

Referente: Andrea Biviano (This email address is being protected from spambots. You need JavaScript enabled to view it.)
Titolo: Finding clusters of galaxies in the Euclid spectroscopic survey

The Euclid satellite has been launched in July 2023. Euclid will identify hundreds of thousands massive clusters of galaxies in the photometric survey. To increase the completeness and reliability of the resulting cluster catalog it is important to use different techniques of cluster detections, exploiting the full capability of the instruments on board Euclid.

The proposed PhD project aims at exploring the possibility of detecting clusters in the Euclid spectroscopic (rather than photometric) survey, by looking at peaks in the redshift distribution of galaxies. The task is not easy because: 1) galaxies that Euclid will detect are mostly emission-line galaxies, and they are not the dominant population of clusters of galaxies; 2) the flux limit of the Euclid survey will not allow to detect very faint emission-line galaxies; 3) the spectral range of the Euclid survey will limit detection to the redshift range 0.9-1.8, where massive clusters are
already predicted to be rare. Nevertheless, the redshift range 0.9-1.8 is particularly interesting as it is beyond the redshift range where clusters are effectively detected by other means - weak lensing and X-ray.

The PhD project will develop the algorithm for the spectroscopic detection of clusters, possibly based on already existing algorithms for the characterization of the mean cluster redshift, and the detection of clusters in the photometric survey. It will then test the algorithm on mock surveys available to the Euclid consortium, obtained from numerical cosmological simulations, that reproduce the Euclid survey to great detail. This test will determine the completeness and reliability of the cluster detection as a function of cluster parameters such as mass and redshift. As
the first data of Euclid will become available (end 2024) the already developed cluster finding routine will be applied on new real data, and a catalog of clusters will be delivered.