THE QUaD GALACTIC PLANE SURVEY. I. MAPS AND ANALYSIS OF DIFFUSE EMISSION

We present a survey of similar to 800 deg(2) of 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 GHz, with spatial resolution of 5' and 3'.5, respectively. Two regions are covered, spanning approximately 245 degrees-295 degrees and 315 degrees-5 degrees in the galactic longitude l and -4 degrees < b < +4 degrees in the galactic latitude b.At 0 degrees.02 square pixel size, the median sensitivity is 74 and 107 kJy sr(-1) at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy sr-1 for Q and U. In total intensity, we find an average spectral index of alpha = 2.35 +/- 0.01 (stat) +/- 0.02 (sys) for vertical bar b vertical bar <= 1 degrees, 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 (vertical bar b vertical bar <= 1 degrees) yields mean spectral indices of alpha(s) = -0.32 +/- 0.03 and alpha(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%.