A Limit on the Large Angular Scale Polarization of the Cosmic Microwave Background

We present an upper limit on the polarization of the cosmic microwave background (CMB) at 7° angular scales in the frequency band between 26 and 36 GHz, produced by the Polarization Observations of Large Angular Regions experiment. The campaign produced a map of linear polarization over the right ascension range 112°-275° at declination 43°. The model-independent upper limit on the E -mode polarization component of the CMB at angular scales l = 2-20 is 10 μK (95% confidence). The corresponding limit for the B -mode is also 10 μK. Constraining the B -mode power to be zero, the 95% confidence limit on E -mode power alone is 8 μK.