  We have used the seven year Wilkinson Microwave Anisotropy Probe (WMAP) data
in order to update the measurements of the intensity signal in the G159.6-18.5
region within the Perseus Molecular Complex, and to set constraints on the
polarization level of the anomalous microwave emission in the frequency range
where this emission is dominant. At 23, 33 and 41 GHz, we obtain upper limits
on the fractional linear polarization of 1.0, 1.8 and 2.7% respectively (with a
95 per cent confidence level). These measurements rule out a significant number
of models based on magnetic dipole emission of grains that consist of a simple
domain (Draine & Lazarian 1999) as responsible of the anomalous emission. When
combining our results with the measurement obtained with the COSMOSOMAS
experiment at 11 GHz (Battistelli et al. 2006), we find consistency with the
predictions of the electric dipole and resonance relaxation theory (Lazarian &
Draine 2000) at this frequency range.
