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--- 20180420_pysm_smooth [2018/04/20 11:18] – created pryke
+++ 20180420_pysm_smooth [2018/04/20 11:51] (current) – pryke
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 We wish to use PySM maps for PICO sims.
 (See [https://arxiv.org/abs/1608.02841 PySM paper] and [https://github.com/bthorne93/PySM_public git repo].)
+PySM can be run at any nside up to 512. What it does internally when asked for <512 I have not investigated. I suspect it downgrades the templates with which it is working. It can also be told to smooth the output maps to a given beam size.
+To be realistic we would generate PICO maps with the resolution varying by band as per [[imageroptions]].
+However, it appears PySM applies the requested smoothing in harmonic space and, because the dynamic
+range of the foreground maps is large, such smoothing is problematic.
+Here is the PySM map at 150 GHz for model a2d4f1s3 in T:
+{{:20180420_fig1.gif}}
+Now I turn on smoothing with 120 arcmin kernel and take the difference of smoothed minus unsmoothed:
+{{:20180420_fig2.gif}}
+We see severe artifacts which results from the harmonic space manipulation of a map which has bright galactic plane.
+The dynamic range is smaller in polarization but there is still a problem.
+We need to decide how to deal with this. Some options
+) The galactic plane will always get masked in post analysis anyway - we could just pre-mask it before smoothing (this is what I did for CMB-S4 sims concerned only with small patch at high latitude.
+) We could do some preliminary nside=16 sims with no smoothing at all.
+) We could implement a map space smoothing which will not suffer from such artifacts.
+There must be knowledge from Planck on how to deal with smoothing a map with large dynamic range - since this is true for the real maps?!

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