Foreground Data

Foreground Overview

Plot of Anisotropy vs. Frequency

Galaxies emit microwave radiation that can interfere with observations of the CMB anisotropy. Fortunately there is a local minimum in the galactic emission near 70 GHz where the CMB signal is relatively bright compared to the galactic signal. The figure above, from Bennett et al., 2013, shows the rms anisotropy as a function of frequency from the CMB (red line) and sources of foreground emission: synchrotron, free-free, spinning dust, and thermal dust emission. The lower and upper curves for each foreground component show the anisotropy for two sky cuts, retaining 77% and 85% of the sky respectively. This figure is available on our foreground image page.

One frequently used technique for removing Galactic foregrounds is to use existing Galactic maps as foreground emission templates and scale assuming a frequency dependence. Such templates are available in the Data Products section, generally as maps stored in nested HEALPix pixelization.

Models of the foreground emission also exist, either resulting from studies at specific frequencies (e.g., see the foreground data product listings for WMAP and COBE/DMR), or presented as generalized software for a variety of applications (e.g., WOMBAT foreground tools).

In addition to maps of diffuse emission, the Products section provides links to a number of Point Source catalogs. Pixels contaminated by bright resolved sources can be masked; residual contamination from unresolved sources may be estimated or modeled.

The following external links also address foreground removal and/or modelling:

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