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Advances in Astronomy
Volume 2012 (2012), Article ID 124931, 6 pages
http://dx.doi.org/10.1155/2012/124931
Research Article

On the Limitations of the Anomalous Microwave Emission Emissivity

1Spitzer Science Center, Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
2NASA Herschel Science Center, Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
3Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK

Received 13 August 2012; Revised 12 October 2012; Accepted 7 November 2012

Academic Editor: Laurent Verstraete

Copyright © 2012 Christopher T. Tibbs et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Many studies of anomalous microwave emission (AME) have computed an AME emissivity to compare the strength of the AME detected in different regions. Such a value is usually defined as the ratio between the intensity of the AME at 1 cm and the thermal dust emission at 100 μm. However, as studies of Galactic dust emission have shown, the intensity of the thermal dust emission at 100 μm is strongly dependent on the dust temperature, which has severe implications for the AME emissivity defined in this way. In this work, we illustrate and quantify this effect and find that the AME emissivity decreases by a factor of 11.1 between dust temperatures of 20 and 30 K. We, therefore, conclude that computing the AME emissivity relative to the 100 μm emission does not allow for accurate comparisons between the AME observed in different environments. With this in mind, we investigate the use of other tracers of the dust emission with which to compute the AME emissivity and we ultimately conclude that, despite the difficulty in deriving its value, the column density of the dust would be the most suitable quantity with which to compute the AME emissivity.