Seminário: Weak lensing analysis of galaxy associations

 

 

Weak gravitational lensing is an important technique to estimate the mass of galaxy associations such as clusters and groups. However, the distortion imprint on the shape of the background galaxies is not only affected by the gravitational field of the main lens, but also affected by all the mass content along the line of sight. This represents a problem when analyzing weak lensing data of low-mass systems such as galaxy groups but also high redshift objects. In this seminar I will revise how weak lensing measurements of galaxy groups are affected by the presence of line-of-sight objects and by the distant large scale structure of the Universe, compromising their mass estimates. The results of this work are based on COSMOS shear mock data. We find that within r200, the LSS contamination can represent up to 20% of the shear signal of the galaxy groups when they are considered isolated in the sky. One way to eliminate this bias is by stacking the mass-excess density profile of several groups and obtain averaged masses of ensemble of groups. Moreover, because individual weak lensing mass measurements of galaxy clusters show scatter with respect to underlying mass due to correlated substructures and triaxial symmetry, the stacking approach can also be used to estimate averaged masses of galaxy clusters. In this seminar I will further discuss how the stacking approach of clusters of galaxies can be applied in the field of cosmology, in particular how averaged masses of clusters will be used to computed the mass function using the CODEX sample.