CONICET | Buscador de Institutos y Recursos Humanos

The nature of the dominant component of galaxies and clusters remains unknown. While the astrophysics comunity supports the cold dark matter (CDM) paradigm as a clue factor in the current cosmological model, no direct CDM detections have been performed. Recently, Faber and Visser (2006) have suggested a simple method for measuring the dark matter equation of state. By combining kinematical and gravitational lensing data it is possible to test the widely adopted assumption of pressureles dark matter. According to this formalism, we have measured the dark matter equation of state using improved techniques and observations and we have found that it does not behaved as expected. In the light of this result, we can now suggest that our understanding of the gravitational processes involved in structure formation is incomplete unless a complete general relativistic analysis is used. We have tested our techniques using simulations and we have also analyzed possible sources of errors that could invalidate or mimic our results.