Galactic foreground contribution to the BEAST CMB 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 H$\alpha$ map, a de-striped version of the Haslam et al. 408 MHz map, and a combined 100 $\mu$m IRAS/DIRBE map. Our analysis samples the BEAST $\sim {10}^{\circ }$ declination band into 24 one-hour (RA) wide sectors with $\sim 7900$ pixels each, where we calculate: (a) the linear correlation coefficient between the anisotropy maps and the templates; (b) the coupling constants between the specific intensity units of the templates and the antenna temperature at the BEAST frequencies and © 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 $8.3\pm 0.4$ $\mu$K/R, and 67.4% dust with $45.0\pm 2.0$ $\mu$K/(MJy/sr). In the Q-band the corresponding values are of 64.4% free-free with $4.1\pm 0.2$ $\mu$K/R and 67.5% dust with $24.0\pm 1.0$ $\mu$K/(MJy/sr). 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 $\mid$b$\mid ={14.6}^{\circ }$ region. By performing the same correlation analysis as a function of Galactic scale height, we conclude that the region within $b=\pm {17.5}^{\circ }$ should be removed from the BEAST maps for CMB studies in order to keep individual Galactic contributions below $\sim 1$% of the map’s rms.