The cored distribution of dark matter in spiral galaxies

International audienceWe present, for five spiral galaxies, HI data which, along with the Halpha rotation curves, are used to derive the distribution of dark matter within these objects. A new method for extracting rotation curves from HI data cubes is presented, which takes into account the existence of a warp and minimizes projection effects. The rotation curves obtained are tested by taking them as input in the construction of model data cubes that are compared with the observed ones: the agreement is excellent. Model data cubes built using rotation curves obtained with standard methods, such as the first-moment analysis, however, fail the test. The HI rotation curves agree well with the Halpha data, where they coexist. Moreover, the combined Halpha + HI rotation curves are smooth, symmetric and extend to large radii