The Gould Belt: Structure and Origin

Autor: Fernando Comeron
Rok vydání: 1993
Předmět:
Zdroj: Publications of the Astronomical Society of the Pacific. 105:441
ISSN: 1538-3873
0004-6280
DOI: 10.1086/133172
Popis: The structure of the Gould Belt system of young stars and star formation complexes has been studied, mainly through the use of an extended sample of early-type stars. Statistical derivations of some of the most relevant parameters of the Belt (orientation, spatial extent, stellar content, age) are made, and some large scale trends of the recent history of star formation in the solar neighbourhood are discussed. Special attention is paid to the local kinematics of young objects; the local peculiar kinematics as revealed by anomalous values of Oort constants is fitted by an expansion of the local system along a preferential line, superimposed to the general pattern of galactic rotation. Some other regions with anomalous motions are detected outside the Gould Belt, with strong evidences for a moving group possibly related to the Cygnus Superbubble. Dynamics of the tilted plane containing the Belt implies a very constrained range of possible values for its original orientation. Moreover, indications of a vertical oscillating motion of the ensemble of stars in the Belt have been found, the association to the Belt being supported by the fact that both the oscillation axis and the current state of vertical motion relate well to the overall picture of the Gould Belt. A second part of this work is devoted to a theory on the origin of the Gould Belt. We propose it to have formed from the collision of a high velocity c loud on the galactic disk by the large scale phase transition of the galactic interstellar medium triggered by the colliding cloud. Analytic 1-D calculations provide us with the values of the most relevant quantities involved in the shock. 2-D computer simulations show the morphology of the region affected by the shock. The stability analysis of the shocked material shows that the unstable regions should have characteristics and locations similar to those of currently observed complexes belonging to the Gould Belt. The galactic magnetic field is essential in determining the further evolution of the shocked material. An overall agreement is found between the observation of structures belonging to the Belt and the predictions of our model.
Databáze: OpenAIRE
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