  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.
