Distances and Kinematics of Gould Belt Star-forming Regions with Gaia DR2 Results

We present an analysis of the astrometric results from Gaia second data release (DR2) to Young Stellar Objects (YSOs) in star-forming regions related to the Gould Belt. These regions are Barnard 59, Lupus 1 to 4, Chamaeleon I and II, $\epsilon$-Chamaeleontis, the Cepheus flare, IC 5146 and Corona Australis. The mean distance to the YSOs in each region are consistent with earlier estimations, though a significant improvement to the final errors was obtained. The mean distances to the star-forming regions were used to fit an ellipsoid of size $(358\pm7)\times(316\pm13)\times(70\pm4)$ pc, and centered at $(X_0,Y_0,Z_0)=(-82\pm15, 39\pm7, -25\pm4)$ pc, consistent with recently determined parameter of the Gould Belt. The mean proper motions were combined with radial velocities from the literature to obtain the three dimensional motion of the star-forming regions, which are consistent with a general expansion of the Gould Belt. We estimate that this expansion is occurring at a velocity of $2.5\pm0.1$ km s$^{-1}$. This is the first time that YSOs motions are used to investigate the kinematic of the Gould Belt. As an interesting side result, we also identified stars with large peculiar velocities.