The QUaD Galactic Plane Survey 1: Maps And Analysis of Diffuse Emission

Abstract

We present a survey of ∼ 800 square degrees of the galactic plane observed with the QUaD telescope. The primary product of the survey are maps of Stokes I, Q and U parameters at 100 and 150 GHz, with spatial resolution 5 and 3.5 arcminutes respectively. Two regions are covered, spanning approximately 245 − 295◦and 315 − 5 ◦in galactic longitude l, and −4 < b < +4 ◦in galactic latitude b. At 0.02◦ square pixel size, the median sensitivity is 74 and 107 kJy/sr at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy/sr for 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 WMAP 5-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 αs = −0.32 ± 0.03 and αd = 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 attributed largely 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 WMAP W band, the latter giving 1.1±0.4%.