37 research outputs found
Gould's Belt
The local velocity patterns of star forming regions, young OB stars, nearby
OB associations, atomic and molecular gas are confronted with models of an
expanding region. We test free expansion from a point or from a ring, expanding
2D shell, and expanding 3D belt with abrupt or gradual energy injection
snow-plowing the ambient medium with or without the drag forces including
fragmentation and porosity of the medium. There is no agreement on the
expansion time, which varies from 30 - 100 Myr. The inclination of the Gould
belt is not explained by the above models of expansion. An oblique impact of a
high velocity cloud may explain it, but the observed velocity pattern is
difficult to reproduce. The Gould's belt may be one of the many structures
resulting from shell-shell collisions in the galactic plane. The origin of the
Gould's belt may be connected to instabilities in the curling gas flows
downstream from the Galaxy spiral arms, forming ISM clouds and star formation
complexes.Comment: 10 pages, 5 figures, Lessons from the Local Group: A Conference in
Honour of David Block and Bruce Elmegreen, Springe
On the hydrodynamics of the matter reinserted within superstellar clusters
We present semi-analytical and numerical models, accounting for the impact of
radiative cooling on the hydrodynamics of the matter reinserted as strong
stellar winds and supernovae within the volume occupied by young, massive and
compact superstellar clusters. First of all we corroborate the location of the
threshold line in the mechanical energy input rate vs the cluster size plane,
found by Silich et al. (2004). Such a line separates clusters able to drive a
quasi-adiabatic or a strongly radiative wind from clusters in which
catastrophic cooling occurs within the star cluster volume. Then we show that
the latter, clusters above the threshold line, undergo a bimodal behavior in
which the central densest zones cool rapidly and accumulate the injected matter
to eventually feed further generations of star formation, while the outer zones
are still able to drive a stationary wind. The results are presented into a
series of universal dimensionless diagrams from which one can infer: the size
of the two zones, the fraction of the deposited mass that goes into each of
them and the luminosity of the resultant winds, for clusters of all sizes and
energy input rates, regardless the assumed adiabatic terminal speed V_A.Comment: 18 pages, 6 figures, accepted for publication in Ap