Hidrógeno atómico en Scorpius y en Ophiuchus

Abstract

We mention new observations of a feature of filamentary shape in the region 350° ≥ l ≥ 338°, at positive latitudes. Its radial velocity and its distance are -12 km/s and 170 pc respectively. We also re-discuss Sancisi's (1974) model of the spatial configuration and the kinematics of the gas, dust and stars in the region of the young association Sco OB2. We conclude that the HI-ridge of high intensity, positive velocity and low velocity dispersion described by Sancisi is part of the extensive HI-ridge associated with Gould's belt. We propose that the Sco OB2 association originated in Gould's belt main expanding gas shell about 2x10⁷ years ago (Blaauw 1964). Later on along its evolution, one or more supernova explosions produced part of a loop of positive velocities, as well as a negative velocity gas complex of which the cloud at v= -12 km/s is a part. All this gas would have been swept off from Gould's belt main expanding shell, which was strongly perturbed, showing presently a remarkable velocity shift as compared to the neighbourhood where there is no association. Besides, it presents a remarkable blank of gas centered at l=341°, b=18°, presumably also produced by stars of the association. As the paper will be published elsewhere, we give here only a synthesis.