Until now, satellite galaxies models assumed that the radiation leading to the photo-evaporation of their gas was produced collectively by the large galaxies nearby, resulting in a quasi-uniform background at the scale of the Milky Way. The new model built by the two french researchers proves this assumption wrong. It is based on a high resolution numerical simulation (the Via Lactea II) describing the dynamics of the dark matter haloes that populated our galaxy and its neigbourhood from the Big Bang to present times. This dataset is completed by a description of the formation of stars from the gas trapped in these haloes, and in paricular a detailed model of the reaction of this gas to UV radiation.
It is the first time that a model accounts for the effect of the radiation emitted by the first stars formed at the center of the Milky way, on its satellite galaxies. Indeed, contrary to previous models, the radiation field produced in this configuration is not uniform, but decreases in intensity as one moves away from the source. On one hand, the satellite galaxies close to the galactic center see their gas evaporate very quickly. They form so few stars that they can be undetectable with current telescopes. On the other hand, the more remote satellite galaxies experience on average a weaker irradiation. Therefore they manage to keep their gas longer, and form more stars. As a consequence they are easier to detect and appear more numerous.
The LIDAU project is funded by the french Agence Nationale pour la Recherche (ANR). The collaboration comprises the 2 researchers from Observatoire Astronomique de Strasbourg, as well as Benoit Semelin, Patrick Vonlanthen et Kenji Hasegawa, who belong to LERMA (Observatoire de Paris).
The missing satellite problem: