Gould’s Belt and Supershells

Abstract

New methods of analysing various observational data will be used to delineate spatial structures that are present in the interstellar medium (ISM) in the local galactic neighborhood, which is here defined to encompass a region centered on the Sun and extending to a distance of approximately 500 parsecs.

The major features in the distribution of the ISM in the northern local galactic neighborhood are two ‘holes’ (regions of low gas density). One of these, in the direction l = 330°, is a bubble created by the Sco- Cen Association. The specific observational phenomena that characterize the l = 330° region can be traced to the Sco-Cen Association and super novae that have occurred within it. The second and larger hole in the local ISM is in the direction l = 150° and probably originated from an earlier, now disintegrated, association located in that region. Violent motions in the gas (observed negative velocities up to 200 km/sec) in a broad region of the sky centered at l = 150° can be traced to a supernova whose shell is well delineated in the neutral hydrogen.

The local ISM in the southern galactic hemisphere is much more uniformly distributed than the gas in the northern hemisphere. However, a significant disturbance of the ISM in the southern hemisphere (a disturbance of much greater spatial extent than heretofore realized) can be directly traced to the Orion complex. The structures in the local ISM suggest some speculations on the nature of Gould’s Belt.