Análise das evidências da matéria escura: perfis de densidade em curvas de rotação galácticas

Abstract

Recent observational data suggest that, from the total content of the universe, ∼ 26% is in the form of the so-called Dark Matter (DM). At present, there is no settled understanding of its nature. On the other hand, galactic structures are important sources of study because their presence strongly inuences both their formative and evolutionary histories. Photometric measurements of the luminous component of a galaxy reveal the distribution of baryonic material. We can infer its dynamics through Newton's laws, however, in strong disagreement with that obtained via spectroscopy (Doppler eect of spectral lines, usually HI clouds). In addition to galaxy rotation curves, other phenomena such as galaxy motion in clusters and gravitational lenses are also studied in the search for a denitive answer. From the well known distributions of DM density proles, two are the best known: • Navarro-Frenk-White (NFW) • Pseudo-Isothermal Sphere Assuming both of them, the rate of rotation of the galaxy halo can be compared with those obtained by spectroscopy. We perform this test for purely baryonic, baryonic + NFW, and baryonic + PSE models using a carefully chosen sample composed of 18 gala- xies. Our results indicate that for the high surface brightness galaxies, the pure baryonic model is a very good approximation, while for the low surface brightness, NFW represents the best one.