Speaker
Description
The emission budget from astrophysical sources at microwave frequencies is mostly dominated by the well-studied and well-understood free-free, synchrotron, and thermal dust emission. Nevertheless, observations mainly carried out in our Galaxy have revealed an unexpected excess of emission (Anomalous Microwave Emission, AME) in the microwave band that cannot be explained by standard emission mechanisms or in terms of the cosmic microwave background (CMB). Its physical origin is not fully understood yet, but the most convincing models predict that AME is dominated by electric dipole emission from rapidly rotating small dust grains, spinning dust, although current observations remain inconclusive.
With the extension of SKA1-MID beyond 15GHz, at frequencies where AME appears to increase with frequency and peak, we have a unique possibility to shed light on AME mechanisms using high angular resolution, polarization and spectroscopic informations which cannot be reached otherwise. Also, while waiting for the approval of band 6, and given the angular resolution achievable by SKA, a striking scientific goal would be the observation of AME in redshifted sources up to z=1 or 2. This would be observable with MID Band 5a (4.6 - 8.5 GHz) or 5b (8.3 - 15.3 GHz). It should be stressed, in fact, that Inter Stellar Medium structures emit over a wide range of scales allowing SKA1-MID observations to focus, with its high angular resolution, on regions with signifcant dust column densities. This will be possible taking advantage of the exibility in terms of u-v coverage (including both short and long baselines) of SKA. Among possible targets that would fit the extended band 6 SKA1-MID in terms of frequency and baseline coverage, we list: molecular clouds, photodissociation regions, dense pre-stellar cores, proto-planetary circumstellar disks, as well as external galaxies.
Progress in this field requires new observations of large heterogeneous samples of AME detections covering ~1-30 GHz, where AME spectrum rises. To this end, we foresee synergies with existing facilities monitoring different angular scales with different resolutions such as the SRT already used for AME science and that could represent the pathfinder for possible extended SKA1-MID follow-up observations.
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