Kinematics of Gould's belt: Model and observations

Using the available data for nearby stars we derive the velocity ellipsoid of dwarf O-B5.5 stars belonging to the Gould Belt (GB). The resulting verte x deviation for the whole sample is negative (l(v) approximate to -70 degre es) and this value is modified to l(v) approximate to 20 degrees when the m embers of the Pleiades moving group are removed from the sample. This impli es the existence of, at least, two different kinematic groups defining the GB system. We also model the evolution of a supershell in the solar neighbo rhood, and obtain a fit to the shape and kinematics of the gas in GB. Assum ing that the expanding shell is also forming stars, we obtain the correspon ding velocity fields for the shell and its newly formed stars. The average vertex deviation value resulting from these models for the new stars is l(v ) approximate to 20 degrees, and is consistent with the observed value when the Pleiades moving group members are excluded from the GB.