Dissertation Defense: “Matéria escura e luminosa de lentes gravitacionais galácticas”

Resumo: Using spectroscopic data from 21 strong gravitational lenses obtained with the SOAR telescope, the relationships between luminous and dark masses of early-type galaxies were studied. By using the pPXF code, velocity dispersions σ_v were found ranging from 174 to 418 km/s, at z ≈ 0.2—0.6. These values were used to test General Relativity through the inference of the post- Newtonian parameter γ, which quantifies the curvature of spacetime caused by a unit of mass. Through stellar population fitting, it was possible to infer stellar mass, age, and metallicity of the sample. The analysis revealed the following information about the lenses, most of which are elliptical galaxies: (1) the σ_v values, combined with masses derived from strong gravitational lensing, led to the inference of γ, which is consistent with general relativity within the uncertainty found; (2) the M⋆/L_r ratio of the sample decreases with increasing redshift, evolving with ⟨d log(M⋆/L_r)/dz⟩ = -0.47 ± 0.21, where (M⋆/L_r)_0 = 7.87 ± 1.67 h_67.3 M⊙/L_r,⊙. This relation is consistent with the scenario of intense past star formation in elliptical galaxies and a passive evolution over time; (3) the projected dark matter fraction within the Einstein radius ranges from f_DM = 0.53—0.98. The analysis revealed that the strong lensing sample consists of extremely massive objects with a significant dark matter fraction.