The calibration of a cosmic balance

Have you ever weighed yourself on a scale at a friend's house and discovered a weight a little different from what you read on the scale at home? It is probably not your weight that has changed but it is one of the two scales (or both) that is not well calibrated. The calibration of a cosmic balance is what an Italy-Argentina collaboration, that includes three astronomers from INAF-OATs, has achieved.

The cosmic balance analyzed is a method, called 'MAMPOSSt' of measuring the mass distribution within clusters of galaxies, designed eight years ago by an INAF-OATs astronomer in collaboration with two French astronomers. This method is based on the spatial distribution and the velocities of cluster galaxies, and it has been extensively used on real data sets.

However, to calibrate the method it is necessary to know the values of the parameters one is trying to measure. For this reason, the research group used cosmological computer simulations of galaxy clusters made by a group led by an astronomer from INAF-OATs.

The calibration carried out will have particular relevance for constraining cosmological models of the universe by means of the mass function of clusters of galaxies, and the properties of dark matter by the analysis of cluster mass density profiles. Furthermore, since the MAMPOSSt mass estimate depends on the orbital parameters of the galaxies, the calibration carried out will allow us to better understand the evolution of galaxies as they wander around in clusters.