July 14th, 2019 - CIB Smoothing: Iterations

Yesterday, Pavel mentioned that it is odd that smoothing the CIB with 12" and 5" beams seems to have almost the same effects. Thus, I tried smoothing the two maps with different iterations (healpy.smoothing has a parameter called 'iter', where the number of iterations can be changed).

Histograms (Left: 12", Right: 5")

It is hard to see any difference between the iter = 3 - smoothed maps and iter = 1 - smoothed maps.

Histogram Differences

I tried plotting the differences between the two histograms (iter = 3 - iter = 1)

Histogram Fractional Differences

Here are the fractional differences of the histograms.

While they fluctuate around zero for both, the fractional differences are clearly non-zero and become larger as [math]\displaystyle{ \ell }[/math] increase.

Cartview

1. lon = [0, 0.5], lat = [0, 0.5], min = 0.1, max = 0.8

-12"

-5"

Again, it is impossible to see the difference in the maps with the given parameters.

2. lon = [-75.5, -75], lat = [-75.5, -75], min = 0.3, max = 0.4

-12"

-5"

When the parameters are set differently however, (by changing the min and max in particular) we see that all four maps are slightly different.

Conclusion

Although changing the number of iterations change the smoothing noticeably (presumably on the 3-point function as well), this effect seems to be quite small to give clues on differentiating the 12" smoothed and 5" smoothed maps.