Galactic Foreground Contribution to the BEAST Cosmic Microwave Background Anisotropy Maps

We report limits on the Galactic foreground emission contribution to the Background Emission Anisotropy Scanning Telescope (BEAST) Ka- and Q-band CMB anisotropy maps. We estimate the contribution from the cross-correlations between these maps and the foreground emission templates of an Hα map, a destriped version of the Haslam et al. 408 MHz map, and a combined 100 μm IRAS DIRBE map. Our analysis samples the BEAST ∼10° declination band into 24 one-hour (R.A.) wide sectors with ∼7900 pixels each, where we calculate (1) the linear correlation coefficient between the anisotropy maps and the templates; (2) the coupling constants between the specific intensity units of the templates and the antenna temperature at the BEAST frequencies; and (3) the individual foreground contributions to the BEAST anisotropy maps. The peak sector contributions of the contaminants in the Ka-band are of 56.5% free-free with a coupling constant of 8.3 ± 0.4 μK R-1, and 67.4% dust with 45.0 ± 2.0 μK MJy-1 sr-1. In the Q band the corresponding values are of 64.4% free-free with 4.1 ± 0.2 μK R-1 and 67.5% dust with 24.0 ± 1.0 μK MJy-1 sr-1. Using a lower limit of 10% in the relative uncertainty of the coupling constants, we can constrain the sector contributions of each contaminant in both maps to <20% in 21 (free-free), 19 (dust), and 22 (synchrotron) sectors. At this level, all these sectors are found outside of the ∣ b ∣ = 14.°6 region. By performing the same correlation analysis as a function of Galactic scale height, we conclude that the region within b = ±17.°5 should be removed from the BEAST maps for CMB studies in order to keep individual Galactic contributions below ∼1% of the map's rms.