Modeling the mass distribution of a pair of galaxy groups

Erick Cignachi (UFRGS)
Abstract: Galaxy groups are important for studying the formation of structures in the Universe. They act as evolutionary bridges between individual galaxies and large clusters of galaxies, providing greater understanding of how the major structures of the Universe are formed and evolve. In this context, we study the HELMS18 system, which is composed of two groups of galaxies along the line of sight, with their respective central galaxies being an early-type galaxy (ETG) and a quasar (QSO), both at z=0.6. These groups are gravitationally lensing a submillimeter galaxy at z=2.39. In this work, our aim is to determine the members of each group and investigate the possible interaction between these structures. To do this, we used multi-object spectroscopy data from GMOS/Gemini to analyze the stellar kinematics of the central galaxies and measure the redshifts of the field galaxies. With the redshifts, we used two methods to identify the members of each group that differ from each other in a member galaxy for the highest z group. We present the findings on the properties of galaxy groups using the two grouping methods, including their spatial distribution and masses. furthermore, we calculate the probability of interaction between the groups using a two-body model, which indicates a probability of 47% or 58% depending on the grouping method. We also present the properties of the central galaxies, such as velocity dispersion and stellar mass. As current work, we are combining these results with those from gravitational lensing analysis to obtain a complete description of these galaxy groups.