The QUaD galactic plane survey. I. maps and analysis of diffuse emission

We present a survey of ∼800 deg²of the galactic plane observed with the QUaD telescope. The primary products of the survey are maps of Stokes I, Q, and U parameters at 100 and 150 GH_z, with spatial resolution of 5′ and 3′5, respectively. Two regions are covered, spanning approximately 245°-295deg; and 315deg;-5deg; in the galactic longitude l and-4° < b < +4° in the galactic latitude b. At 0°.02 square pixel size, the median sensitivity is 74 and 107 kJy sr ^-1at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy sr^-1for Q and U. In total intensity, we find an average spectral index of α = 2.35 ± 0.01 (stat) ± 0.02 (sys) for |b| ≤ 1°, indicative of emission components other than thermal dust. A comparison to published dust, synchrotron, and free-free models implies an excess of emission in the 100 GHz QUaD band, while better agreement is found at 150 GHz. A smaller excess is observed when comparing QUaD 100 GHz data to the WMAP five-year W band; in this case, the excess is likely due to the wider bandwidth of QUaD. Combining the QUaD and WMAP data, a two-component spectral fit to the inner galactic plane (|b| ≤ 1°) yields mean spectral indices of α_s=-0.32 ± 0.03 and α_d= 2.84 ± 0.03; the former is interpreted as a combination of the spectral indices of synchrotron, free-free, and dust, while the second is largely attributed to the thermal dust continuum. In the same galactic latitude range, the polarization data show a high degree of alignment perpendicular to the expected galactic magnetic field direction, and exhibit mean polarization fraction 1.38 ± 0.08 (stat) ± 0.1 (sys)% at 100 GHz and 1.70 ± 0.06 (stat) ± 0.1 (sys)% at 150 GHz. We find agreement in polarization fraction between QUaD 100 GHz and the WMAP W band, the latter giving 1.1% ± 0.4%.