New constraints on the polarization of the Anomalous Microwave Emission from QUIJOTE

In this article we present an analysis of the Anomalous Microwave Emission (AME) towards the region G159.6-18.5, located in the Perseus molecular complex. This is one of the most studied AME regions in the sky. The new QUIJOTE data at 10-20 GHz allow us to confirm the downturn of the AME spectrum at frequencies below 20 GHz, first discovered in this region in previous data from the COSMOSOMAS experiment.

This decrease of flux at low frequencies is predicted by models based on electric dipole emission from spinning dust grains, nowadays the best hypothesis to explain the origin of this emission. The AME spectrum presented in this article is the most precise ever measured, with 13 data points dominated by this kind of emission, and we use it to fit some physical parameters on which the spinning dust emission depend. From the QUIJOTE polarization data, we derive upper limits on the polarization fraction of the AME in the frequency range 10-20 GHz. Studies of this kind are essential to discriminate between electric dipole emission and other alternative models that predict different levels of polarization degrees.


Constraints (95% C.L.) on several microwave emission models based on our upper limits on G159.6-18.5 (black dots) and on others in dierent regions from the literature (Mason et al. 2009; Battistelli et al. 2006; Lopez-Caraballo et al. 2011; Dickinson et al. 2011; Rubiño-Martín et al. 2012b). The black lines are theoretical predictions for the frequency dependence of the fractional polarization of the electric dipole (ED) emission from Lazarian & Draine (2000) (dashed line) and Hoang et al. (2013) (solid line). The red and blue lines correspond to the models of Draine & Lazarian (1999) for the magnetic dipole (MD) emission. The dierent lines correspond to dierent grain compositions and geometries. The observations are generally consistent with the electric dipole emission models, and rule out the models for the fractional polarization of the magnetic dipole emission.

Further details in