Instrument, method, brightness, and polarization maps from the 2003 flight of BOOMERanG

Aims. We present the boomerang-03 experiment, and the maps of the Stokes parameters I, Q, U of the microwave sky obtained during a 14 day balloon flight in 2003. Methods. Using a balloon-borne mm-wave telescope with polarization sensitive bolometers, three regions of the southern sky were surveyed: a deep survey (similar to 90 square degrees) and a shallow survey (similar to 750 square degrees) at high Galactic latitudes ( both centered at RA similar or equal to 5.5h, Dec similar or equal to - 45 degrees) and a survey of similar to 300 square degrees across the Galactic plane at RA similar or equal to 9.1h, dec similar or equal to - 47 degrees. All three surveys were carried out in three wide frequency bands centered at 145, 245 and 345 GHz, with an angular resolution of similar to 10'. Results. The 145 GHz maps of Stokes I are dominated by Cosmic Microwave Background ( CMB) temperature anisotropy, which is mapped with high signal to noise ratio. The measured anisotropy pattern is consistent with the pattern measured in the same region by boomerang-98 and by WMAP. The 145 GHz maps of Stokes Q and U provide a robust statistical detection of polarization of the CMB when subjected to a power spectrum analysis. The amplitude of the detected polarization is consistent with that of the CMB in the CDM cosmological scenario. At 145 GHz, in the CMB surveys, the intensity and polarization of the astrophysical foregrounds are found to be negligible with respect to the cosmological signal. At 245 and 345 GHz we detect ISD emission correlated to the 3000 GHz IRAS/DIRBE maps, and give upper limits for any other non-CMB component. When compared to monitors of different interstellar components, the intensity maps of the surveyed section of the Galactic plane show that a variety of emission mechanisms is present in that region.