The State-of-Play of Anomalous Microwave Emission (AME) Research
Anomalous Microwave Emission (AME) is a component of diffuse Galactic radiation observed at frequencies in the range ≈ 10–60 GHz. AME was first detected in 1996 and recognised as an additional component of emission in 1997. Since then, AME has been observed by a range of experiments and in a variety of environments. AME is spatially correlated with far-IR thermal dust emission but cannot be explained by synchrotron or free–free emission mechanisms, and is far in excess of the emission contributed by thermal dust emission with the power-law opacity consistent with the observed emission at sub-mm wavelengths. Polarization observations have shown that AME is very weakly polarized ( ≲ 1 %). The most natural explanation for AME is rotational emission from ultra-small dust grains ("spinning dust"), first postulated in 1957. Magnetic dipole radiation from thermal fluctuations in the magnetization of magnetic grain materials may also be contributing to the AME, particularly at higher frequencies ( ≳ 50 GHz). AME is also an important foreground for Cosmic Microwave Background analyses. This paper presents a review and the current state-of-play in AME research, which was discussed in an AME workshop held at ESTEC, The Netherlands, June 2016.
Additional Information© 2018 Elsevier B.V. Received 10 November 2017, Accepted 22 February 2018, Available online 23 February 2018. We thank Chris Tibbs and colleagues at ESTEC for organising the 3rd AME workshop, held 23–24 June 2016 at ESTEC, Noordwijk, The Netherlands. CD acknowledges support from an STFC Consolidated Grants (ST/P000649/1) and an ERC Starting (Consolidator) Grant (no. 307209). BTD was supported in part by NSF grant AST-1408723. TH acknowledges the support by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (2017R1D1A1B03035359). CTT acknowledges an ESA Research Fellowship. ESB acknowledges support from Sapienza Ateneo projects 2016. AB and TO are supported by JSPS and CNRS under the Japan–France Research Cooperative Program. CHLC thanks CONICYT for grant Anillo ACT-1417. MP acknowledges grant #2015/19936-1, São Paulo Research Foundation (FAPESP). YCP acknowledges support from a Trinity College JRF. FP thanks the European Commission under the Marie Sklodowska-Curie Actions within the H2020 program, Grant Agreement number: 658499-PolAME-H2020-MSCA-IF-2014. JARM acknowledges the funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 687312 (RADIOFOREGROUNDS). This work has been partially funded by the Spanish Ministry of Economy and Competitiveness (MINECO) under the project AYA2014-60438-P. MV acknowledges support from FONDECYT through grant 3160750. We thank George Bendo and Tim Pearson for helpful discussions while preparing the draft. This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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