The interrelationship between cosmic dust and the microwave background |
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Authors: | Paul S Wesson |
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Institution: | (1) St. John's College, Cambridge, England;(2) Institute of Astronomy, Cambridge University, England |
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Abstract: | Attention is given to the radiation of microwaves by charged dust in space. Presently-used particle distributions do not restrict the presence in space of large numbers of small (r<10–6 cm) silicate grains, but it is shown that such densities (![rhov](/content/x4q140262685q860/xxlarge1009.gif) 10–25–10–26 g cm–3) of small grains would produce a microwave background with an energy density of the same order of magnitude as the energy density of the (presumed) cosmological 3 K background. Limits set by the isotropy of the latter are: (HI clouds) 10–26, (Galactic plane) 10–30, (Halo) 10–32, (Local Group) 10–34 g cm–3. These limits imply that either there is a cutoff in particle distributions atr 10–6 cm, or that the density of silicate grains in space has been generally overestimated, or that cosmic rays have broken up a lot of grains so that they now form a population of grains of very small size ( 10–7 cm) which are difficult to detect by conventional methods. One way to look for the latter population is by studying expected distortions of the 3 K spectrum to the short wavelength side of the portion hitherto observed (grains may have a size distribution able to give an approximate black-body curve for radiation from larger grains of 10–6 cm size), and by testing the effective energy density of the 3 K field in other galaxies. |
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