I'm trying to have alms(T,E,B) from map with map2alm,Healpix subroutine.
For simple testing, I put alm=0 except a2,1=1 for temperature and got the proper map but reproduced alms from map2alm,healpix subroutine, haven't got same values like input ones. They have even imaginary part!
Simply speaking,
Input alm =0 or 1
(alm2map) -> Output map ->(map2alm) ->
Output alm = a+bi (nonzero b)
Is there anyone who has a idea?
It seems that imaginary part from ring_analysis for m are nonzero component but still don't know what's wrong with them..
For detail, I used w8ring_TQU=1.d0
zbounds=/-1.d0,1.d0/, Nside=8, nlmax=16
Healpix2.0 map2alm
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- Posts: 5
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- Affiliation: University of Cape Town
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- Posts: 13
- Joined: July 26 2006
- Affiliation: Max-Planck-Institute for Astrophysics
Healpix2.0 map2alm
The map -> a_lm step is not exact for the Healpix pixelisation; this is the case for many sperical grids in practical use.
For your setup I would expect that you should obtain a_lm that differ from the original input by up to 0.001. This can be improved by using anafast's iterative analysis mode.
For your setup I would expect that you should obtain a_lm that differ from the original input by up to 0.001. This can be improved by using anafast's iterative analysis mode.