Paper II: Spinning dust in galaxies

The analysis of the radio spectra presented in this paper was made using the radiospec package, version 1.0. This version of radiospec has facilities for modelling spectra with multiple components including synchrotron, high-opacity free-free and spinning dust.

Title

Anomalous dust emission in NGC 6946

Authors

Anna M. M. Scaife, Bojan Nikolic, Guy G. Pooley, David A. Green, Keith J. B. Grainge, Rainer Beck, Matthew L. Davies, Thomas M. O. Franzen, Michael P. Hobson, Natasha Hurley-Walker, Anthony N. Lasenby, Malak Olamaie, Carmen Rodriguez-Gonzalvez, Richard D. E. Saunders, Paul F. Scott, Timothy W. Shimwell, David J. Titterington, Elizabeth M. Waldram Jonathan T. L. Zwart

Abstract

We report new cm-wave measurements at five frequencies between 15 and 18 GHz of the continuum emission from the reportedly anomalous “region 4” of the nearby galaxy NGC 6946. We find that the emission in this frequency range is significantly in excess of that measured at 8.5 GHz, but has a spectrum from 15-18 GHz consistent with optically thin free-free emission from a compact H II region. In combination with previously published data we fit four emission models containing different continuum components. These fits show that, in combination with data at other frequencies, a model with a spinning dust component is slightly preferred above those which possess more well established emission mechanisms.

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Software

The spectral analysis presented in this paper was done using radiospec version 1.0. You can download the complete software at Download & building of the radiospec package. The complete analysis can be reproduced easily in one step by executing the code in the file apps/n6946.py.

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