Probing the origin of the microwave anomalous foreground

TL;DR

This study investigates the origin of galactic anomalous microwave emission by comparing microwave data with dust IR emission, providing evidence that supports spinning dust models through correlation analyses and model predictions.

Contribution

The paper offers a novel analysis linking microwave anomalous emission to small dust grains and validates spinning dust models by comparing correlations with IR data and radiation field estimates.

Findings

Anomalous emission correlates better with small grain emission at 12 μm than with big grains at 100 μm.

Dividing 12 μm flux by the radiation field G0 improves the correlation, supporting spinning dust models.

Results favor spinning dust as the primary source of the anomalous microwave foreground.

Abstract

The galactic anomalous microwave emission detected between 10 and 90 GHz is a major foreground to CMB fluctuations. Well correlated to dust emission at 100 $\mu$m, the anomalous emission is interstellar but its origin is still debated. Some possible explanations relate it to dust: emission of spinning, small (nanometric) grains carrying a permanent electric dipole or magnetic fluctuations in larger (submicronic) grains. To probe the origin of the anomalous emission, we compare microwave data to dust IR emission and search for specific signatures predicted by models of spinning dust. For the anomalous emission, we use the 23 GHz all-sky map deduced from WMAP data by Miville-Deschenes et al. (2008). The dust emission is traced by IRAS data. Models show that spinning dust emission is little sensitive to the intensity of the radiation field (Go) for 10<nu<30 GHz while the corresponding mid-IR emission is proportional to Go. To test this behaviour in our comparison, we derive Go from the dust temperature maps of Schlegel et al. (1998). From all-sky maps, we show that the anomalous emission is better correlated to the emission of small grains (at 12 $\mu$m) than to that of big grains (at 100 $\mu$m). In addition we show that the former correlation is significantly improved when the 12 $\mu$m flux is divided by Go, as predicted by current models of spinning dust.