Preliminary ILC maps - part 2

 (C. Umilta)

Update (2020-02-06): maps and spectra obtained with ILC have been multiplied twice by the map, but the fky has been corrected as if there has been only one map multiplication. This has been conrrected in later postings. Likely, this is what direves the large difference in the Chile maps, where the apodization is very smooth.


This posting shows preliminary ILC maps created with 06 sims, and follows this previous preliminary posting. Information on DC06 maps can be found here. There are three different sky masks, and two foreground models. I create here ILC maps for the first three sims of each set and compare them with input CMB maps and 95 GHz maps.

For each map set, I compute and store the alm for each frequency, debeam them and rebeam them to a common resolution of 2.3 arcmin (as this is the resolution of the 95 GHz map). I then use these alm to compute the weights and the reconstructed maps. The computation is done with healpy, and the mask used are apodized and shown at the bottom of this posting. Computing and storing the alms is quite expensive (a few Gb per each simulation set) so they need to be deleted after computation.

For each map I show the input and reconstructed ILC map, as well as their difference. It is not clear whether there is an improvement using the ILC map over the 95 GHz map. The patterns of the residuals are very different, but at a very low magnitude.

Figure 1:
Fig. 1 shows the input and reconstructed ILC map (and they difference) for the first three realizations. also shows the 95 GHz map for comparison.

I plot here the spectra of the ILC map and the original map, as well as the 95 GHz spectrum and the ILCxinput spectrum. Mask effects are corrected via a simple fsky scaling, and one can ee how this is defective in the case of the more complicated mask pattern of Chile. All spectra are binned with bin_width=20. For TT spectra, there is virtually no difference betzeen 95 GHz and the ILC spectrum. For EE spectra, one can see a difference above ell=2500. The difference is more visible in BB spectra, but one must note that there is no E-to-B leakage correction in these spectra.

Figure 2:
Fig. 2 shows the input and reconstructed ILC spectra for the first three realizations.

In Figure 3 I show the weights for the ILC in the three different frequencies.

Figure 3:
Fig. 3 shows the weights for the reconstructed ILC.

In Figure 4 I show the apodized masks and the hit maps for the three sky configurations.

Figure 4:
Fig. 4 shows the three masks.