Microwave emission from the Edgeworth-Kuiper Belt and the asteroid belt constrained from the Wilkinson microwave anisotropy probe

Abstract

Objects in the Edgeworth-Kuiper Belt and the main asteroid belt should emit microwaves that may give rise to extra anisotropy signals in the multipole of the cosmic microwave background (CMB) experiment. Constraints are derived from the absence of positive detection of such anisotropies for ℓ ≲ 50, meaning the total mass of Edgeworth-Kuiper Belt objects is smaller than 0.2 M⊕. This limit is consistent with the mass extrapolated from the observable population with the size of a ≳ 15km, assuming that the small-object population follows the power law in size dN/da ∼ a-q with the canonical index expected for collisional equilibrium, q ≃ 3.5, with which 23% of the mass is ascribed to objects smaller than are observationally accessible down to grains. A similar argument applied to the main asteroid belt indicates that the grain population should not increase more quickly than q ≃ 3.6 toward smaller radii, if the grain population follows the power law that continues to observed asteroids with larger radii. Both cases are at or only slightly above the limit that can be physically significant, implying the importance of further tightening the CMB anisotropy limit, which may be attained with observation at higher radio frequencies. © 2011. The American Astronomical Society. All rights reserved.