Mark Walker, Mark Wardle, PASA, 16 (3), 262.
Next Section: Introduction
The Cloudy Universe
Mark Walker & Mark Wardle
Special Research Centre for Theoretical Astrophysics, School of Physics,
University of Sydney, NSW 2006
M.Walker/M.Wardle@physics.usyd.edu.au
Abstract:
Modelling of Extreme Scattering Events suggests that the Galaxy's dark matter is an undetected population of cold, AU-sized, planetary-mass gas clouds. None of the direct observational constraints on this picture - thermal/non-thermal emission, extinction and lensing - are problematic. The theoretical situation is less comfortable, but still satisfactory. Galactic clouds can survive in their current condition for billions of years, but we do not have a firm description for either their origin or their evolution to the present epoch. We hypothesise that the proto-clouds formed during the quark-hadron phase transition, thereby introducing the inhomogeneity necessary for compatibility with light element nucleosynthesis in a purely baryonic universe. We outline the prospects for directly detecting the inferred cloud population. The most promising signatures are cosmic-ray-induced H emission from clouds in the solar neighbourhood, optical and X-ray flashes arising from cloud-cloud collisions, ultraviolet extinction, and three varieties of lensing phenomena.
Keywords: dark matter -- galaxies: halos -- ISM: clouds
- Introduction
- Identification of dark matter
- Extreme Scattering Events
- Compatibility with other data
- Theoretical considerations
- Observational tests
- Theoretical outlook
- Summary
- Acknowledgements
- References
© Copyright Astronomical Society of Australia 1997