L-type ultra-cool dwarfs are known to have a dusty atmosphere. Surface heterogeneities, due to cloud patterns or rotationally-induced oblateness, would result in an imperfect polarization cancellation and a small, but non-zero net polarization. The measurement of linear polarization could shed light on the dust distribution and oblateness of those

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Context. Properties of galaxies depend on their large-scale environment. As the influence of active galactic nuclei (AGN) in galaxy evolution is becoming more evident, their large-scale environments may help us understand the evolutionary processes leading to activity. The effect of activity can be seen particularly by showing whether different

The luminosity function is not only crucial to know the stellar density distribution in space, and thus to know the structure of the Galaxy; it also allows the determination of the stellar mass function using the mass-luminosity relationship. The luminosity and mass functions are crucial to understand star formation and the evolution of the Milky

A subset of microquasars exhibits high peculiar velocity with respect to the local standard of rest due to the kicks they receive when being born in supernovae. The interaction between the radio plasma released by microquasar jets from such high-velocity binaries with the interstellar medium must lead to the production of trails and bow shocks

In the last decade a significant amount of observational effort has been made to determine the physical parameters of low mass stars (M 1 Msol). The most recent observations appear to show a discrepancy between the mass-radius relation predicted by the models and that obtained from the observational data. This discrepancy appear to be explained by