EVOLUÇÃO DE GALÁXIAS EM SUPERGRUPOS DE AGLOMERADOS DE GALÁXIAS EM BAIXO REDSHIFT

Abstract

Supergroups are “groups of galaxy groups” and/or galaxy clusters with substructures that might collapse into a single cluster. Since galaxy clusters have singular characteristics, such as a well-defined red sequence and a concentration of early-type galaxies, it is important to understand how these properties came to be and which factors — such as preprocessing in these structures — might have led to this configuration. There are few studies about Supergroups (e.g., Brough et al., 2006; Sengupta et al., 2022; Smit et al., 2015). Besides, the studies generally focus on the analysis of one Supergroup at a time. In this context, we will study a set of Supergroups over a significant redshift range (z<0.5), expanding the list of these objects, and understanding their common characteristics concerning galaxy evolution and stellar population distribution. We identified Supergroups in the RedMaPPer galaxy clusters catalog using data from the 5,000 sq. deg. DES footprint in the griz bands. We analyzed the galaxy evolution inside them using colors, understanding how factors, such as the radius and the mass of the Supergroup, might influence these populations. To find Supergroups, we searched for cluster overdensities in redshift bins of 0.1 out to z=0.5 and with 5 cMpc wide pixels in RA and Dec. We used the K correction of Blanton and Roweis (2007) to correct the magnitude in all bands and a Gaussian Mixture Model (GMM) to separate populations in blue and red galaxies. We found 8 Supergroup candidates with 0.1<z<0.4 and minimum total mass of 0.5—1.8x10¹⁵ M☉. The member clusters have mgap between the BCG and the fourth-brightest galaxy of less than 2.5, indicating recent or ongoing formation. There is a correlation between the fraction of red galaxies and the radius in individual clusters, as well as in Supergroups. The central clusters have a greater fraction of red in their interior than the satellite clusters. Similarly, more massive Supergroups have a higher red fraction than less massive ones across all radii. Thus, our results indicate that the quenching rate could also be related to the Supergroup’s mass and that galaxies undergo preprocessing in the substructures. supergroups; galaxy:clusters; galaxy:evolution