Differences at low l in Planck's first light sky map of the cosmic microwave background from WMAP's and COBE's

TL;DR

The paper compares the Planck, WMAP, and COBE CMB sky maps, finding significant differences at low multipole moments, and suggests potential reconstruction artifacts in earlier maps, though conclusions are preliminary due to limited sky coverage.

Contribution

It provides an initial comparison of Planck's first light sky map with WMAP and COBE, highlighting discrepancies at low l and potential artifacts in previous reconstructions.

Findings

Significant differences at low l between Planck and WMAP/COBE maps.

Potential reconstruction artifacts identified in WMAP and COBE maps.

Limited sky coverage of Planck data makes conclusions preliminary.

Abstract

The recent release of the first light sky map of the cosmic microwave background (CMB) from the Planck satellite provides an initial opportunity for comparison with the WMAP and COBE sky maps and their reconstruction algorithms. The precision of the match between Planck's and WMAP's anisotropies below several degrees in size, which corresponds to spherical harmonics with high l, provides confidence that the differences between the anisotropies at low l are substantial. If the Planck first light sky map is taken as the gold standard, the results seem to suggest the low l components of the WMAP map and a considerable part of the COBE sky map have a similar reconstruction artefact. As the Planck first light sky map covers only about 10% of the sky, any conclusions drawn from this comparison are speculative but deserving of further investigation.