Astrophys.Journal000,000{000(1995)Printed28September1995 BaryonicDarkHalos:MachosandColdGas?
نویسنده
چکیده
We consider the possibility that the dark matter in the halos of galaxies may be in the form of clusters of Machos within which are embedded cold, dense gas clouds. Mi-crolensing experiments have found evidence that the Galactic halo contains up to half of its mass in the form of low-mass Machos. A number of observational and dynamical arguments point to the existence of hitherto unobserved cold gas around galaxies. We show that the cold gas can be stabilized by Macho clusters. Within the framework of a simple two-component model, we derive constraints on the Macho clusters and on the halo cold gas content. Typical cluster masses are 10 M ; typical Macho masses are 0:01 M ; and the gas content could be up to of order 50 %. Various predictions are given for testing the hypothesis that such objects could constitute most of the mass in the dark halos of galaxies. If halos are indeed baryonic and contain signii-cant amounts of cold gas, they are likely to play a much more active role in galaxy formation and evolution than is commonly supposed.
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