Análise da anisotropia orbital de populações de galáxias em aglomerados

Abstract

In this work we analyze the velocity anisotropy profiles β(r) of the star-forming (SF), transition (T), AGN, and quiescent (Q) galaxy populations belonging to gaussian clusters in order to study the impact of a galaxy’s orbital profile on the inhibition of its star formation process, as well as the triggering or cessation of nuclear activity. Furthermore, we separately analyze the samples of galaxies in gaussian (G) and non-gaussian (NG) clusters to compare their evolutionary stages. For this investigation, we use a sample composed of 177 G clusters and 34 NG clusters, which contain 11195 and 7055 galaxies, respectively. Galaxies belonging to G clusters are classified based on the main mechanism responsible for gas ionization using BPT and WHAN diagnostic diagrams. After normalizing the radial positions and peculiar velocities of the galaxies, we group them into two "pseudo-clusters" called cluster ensembles, separating galaxies belonging to G and NG clusters. The velocity anisotropy profiles were obtained using the MAMPOSSt code and the inversion of the Jeans equations. Our results show that Q galaxies have the smallest projected distances and velocity dispersions, while SF galaxies have the highest values of radial distance and velocity dispersions. T and AGN populations exhibit similar velocity dispersions, although the AGN population is less scattered in the cluster. The profiles of ν(r), σP (R), and β(r) indicate that Q and AGN populations are close to equilibrium, whereas the T population shows some signs of non-equilibrium. The results for the SF population are consistent with an unbalanced population. We interpret these results in a scenario where a population of SF galaxies in infall, hence possessing higher kinetic energies, is affected by environmental mechanisms that transform it into a quiescent population with lower velocity dispersions. A fraction of galaxies in the process of transitioning from SF to Q may trigger nuclear activity due to environmental mechanisms, appearing as a T population with a higher degree of viralization. By separately analyzing the samples of G and NG clusters, we find that galaxies in G clusters have smaller typical distances to the cluster center as well as lower velocity dispersions compared to galaxies in NG clusters. Through the β(r) profiles, we conclude that both populations exhibit some degree of non-equilibrium, although the NG population is certainly less virialized than the G population. Finally, in the case of the G population, we argue that the signs of non-equilibrium are due to the presence of a more recently accreted population (SF).