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Investigating the Source of Planck-Detected AME: High-Resolution Observations at 15?GHz

DOI: 10.1155/2013/354259

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Abstract:

The Planck 28.5?GHz maps were searched for potential Anomalous Microwave Emission (AME) regions on the scale of ~3° or smaller, and several new regions of interest were selected. Ancillary data at both lower and higher frequencies were used to construct spectral energy distributions (SEDs), which seem to confirm an excess consistent with spinning dust models. Here we present higher resolution observations of two of these new regions with the Arcminute Microkelvin Imager Small Array (AMI SA) between 14 and 18?GHz to test for the presence of a compact (~10 arcmin or smaller) component. For AME-G107.1+5.2, dominated by the Hii region S140, we find evidence for the characteristic rising spectrum associated with either the spinning dust mechanism for AME or an ultra- /hypercompact Hii region across the AMI frequency band; however, for AME-G173.6+208 we find no evidence for AME on scales of ~2–10 arcmin. 1. Introduction The Planck satellite [1, 2] observes the sky in nine frequency bands, covering a range from 30 to 857?GHz. Its wide frequency range potentially allows the detection of AME since the high-frequency data above 100?GHz can be used to constrain the thermal emission, while the lower frequency data is close to the theoretical peak of the spinning dust emission. When combined with ancillary data at lower frequencies, the spectra of AME regions can be accurately determined and used to probe their properties on large ( 1 degree) scales. The Planck maps were used to detect several new potential AME regions [3] by subtracting a spatial model of known emission mechanisms (synchrotron, free-free, and thermal dust) extrapolated from observational or theoretical predictions. Two of these regions, AME-G173.6+2.8 and AME-G107.1+5.2, were selected, and ancillary data were used at both higher and lower frequencies to construct SEDs, which contain suggestions of AME consistent with spinning dust emission. The Arcminute Microkelvin Imager Small Array (AMI SA) is a radio interferometer situated near Cambridge, UK. Primarily an SZ survey instrument, the AMI-SA, is specifically designed to have high sensitivity to low-surface-brightness emission on scales of 2–10 arcmin. It operates between 14 and 18?GHz, close in frequency to the theoretical peak of the spinning dust emission, the position of which varies between 10–50?GHz depending on grain size, composition, and ambient conditions. The AMI SA has previously been used both to identify and to characterize spinning dust regions in multiple galactic (e.g. [4, 5]) and extragalactic [6] sources. The higher angular

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