Foreground maps in Wilkinson Microwave Anisotropy Probe frequency bands

Abstract

This paper provides full sky maps of foreground emission in all Wilkinson Microwave Anisotropy Probe (WMAP) channels, with very low residual contamination from the cosmic microwave background (CMB) anisotropies and controlled level of instrumental noise. Foreground maps are obtained by subtraction of a properly filtered CMB map, obtained from linear combinations of needlet-based representations of all WMAP observations and of a inline image map. The error in the reconstructed foreground maps on large scales is significantly lower than the original error due to CMB contamination, while remaining of the order of the original WMAP noise on small scales. The level of the noise is estimated, which permits to implement local filters for maximizing the local signal-to-noise ratio. An example of such filtering, which reduces the small-scale noise using latitude-dependent filters, is implemented. This enhances significantly the contrast of galactic emission, in particular on intermediate angular scales and at intermediate galactic latitude. The clean WMAP foreground maps can be used to study the galactic interstellar medium, in particular for the highest frequency channels for which the proper subtraction of CMB contamination is mandatory. The foregrounds maps can be downloaded from a dedicated website.