How display a mollview projection of CAMB output fits file ?

  • Thread starter fab13
  • Start date
  • #1
188
3

Main Question or Discussion Point

hi,

i want to display into IDL a mollview projection of the output fits file ('test_scalCls.fits') of CAMB program (Code for Anisotropies in the Microwave Background) but can't get it.

I have IDL ASTRO, Healpix_2.11c and WMAP librairies and i tried several things:

1*/

HIDL> mollview, 'test_scalCls.fits', /silent

returns :

% VEC2PIX_RING: Invalid Nside -1
% Execution halted at: VEC2PIX_RING 71 /usr/local/Healpix_2.11c/src/idl/toolkit/vec2pix_ring.pro
% DATA2MOLL 242 /usr/local/Healpix_2.11c/src/idl/visu/data2moll.pro
% MOLLVIEW 492 /usr/local/Healpix_2.11c/src/idl/visu/mollview.pro
% $MAIN$

2*/

read_fits_map, 'test_scalCls.fits', map, hdr, xhdr, NSIDE=nside

It seems i get the data in the "map" array but i don't know how to use these data in order to display a mollview projection.

3*/

I found this thread: https://www.physicsforums.com/showthread.php?t=279764, so i did :

fits_reproj_healpix, 'test_scalCls.fits', 'moll_last.fits', size=1, proj='Mol'

returns :

% FITS_REPROJ_HEALPIX: WARNING - SKYCOORD keyword not found in header
% FITS_REPROJ_HEALPIX: WARNING - Native Galactic coordinates assumed
% GET_HEAL_LUT: Reading the look-up table mollweide_h10s_lut.fits
We do not support the selected resolution...
Number of input pixels: 2001
N_Pixels, Resolution: 2001 -1
% FITS_REPROJ_HEALPIX: Map resolution too high or low for the current look-up tables...
% Execution halted at: FITS_REPROJ_HEALPIX 106 /home/fab/WMAP/pro/fits_reproj_healpix.pro
% FITS_REPROJ_HEALPIX 106 /home/fab/WMAP/pro/fits_reproj_healpix.pro
% $MAIN$

---------------------------------------------------------------------------------------------------------------------------------------

4*/ I tried to display it with mapview but it fails :

HIDL> mapview
% Compiled module: MAPVIEW.
MAPVIEW v1.3 (07 Jul 2004) -- WMAP project HEALPix map viewer
% Compiled module: XREGISTERED.
% Compiled module: NPIX2NSIDE.
Waiting for file name to be input
% Compiled module: LOADCT.
% Compiled module: FILEPATH.
% LOADCT: Loading table RAINBOW
% Compiled module: FSC_FILESELECT.
% Compiled module: CW_BGROUP.
% Compiled module: EULER_MATRIX_NEW.
% Compiled module: HEALPIX_TO_IMAGE.
% Compiled module: GET_HEAL_LUT.
% Compiled module: CONCAT_DIR.
% Compiled module: READFITS.
% Compiled module: SXPAR.
% Compiled module: GETTOK.
% Compiled module: VALID_NUM.
% Compiled module: GET_HEAL_RES.
% Compiled module: XMANAGER.
HIDL>
% Compiled module: VEC2ANG.
% Compiled module: ANG2PIX_NEST.
% Compiled module: NSIDE2NPIX.
% Compiled module: INIT_XY2PIX.
HIDL>
Reading /home/fab/test_scalCls.fits
% Compiled module: FITS_OPEN.
% Compiled module: SXDELPAR.
% Compiled module: FITS_READ.
% Compiled module: FITS_CLOSE.
% Compiled module: TBINFO.
% Compiled module: FXPAR.
0
% Compiled module: TBGET.
% Compiled module: TAG_EXIST.
% Compiled module: LOADCT_012.
% LOADCT: Loading table RAINBOW
We do not support the selected resolution...
Number of input pixels: 2001
Map resolution too high or low for the current look-up tables...
N_Pixels, Resolution: 2001 -1
% Stop encountered: HEALPIX_TO_IMAGE 111 /home/fab/WMAP/pro/healpix_to_image.pro

------------------------------------------------------------------------------------------------------------------------------------

5*/ i tried with skyviewer and ds9 too, in vain.


Thanks for your help !
 

Answers and Replies

  • #2
Chalnoth
Science Advisor
6,195
442
So, it's looking like the data you stored in the "map" file isn't actually a map. With npixels = 2001, I'm willing to bet that this is the power spectrum, not a map (which would make sense, as this is CAMB's primary task).

If you want to display a typical map that you would get from this power spectrum, then you need to do the following:

1. Read in the power spectrum as a power spectrum (not a Healpix map).
2. Generate a random set of alm's from that power spectrum.
3. Perform a spherical harmonic transform to produce the map that is represented by the generated alm's.
4. Display the map.

Now, I don't personally use IDL for these tasks. I instead use the command-line tools offered by Healpix. For example, I would make use of the Healpix synfast program to perform steps 1-3 (you can use the interactive mode or use a parameter file). This will output a Healpix map in .fits format, which can then be displayed. Usually I use the map2tga program that comes with the Healpix C++ code, though map2gif will work just as well, as will the mollview code you have above.
 

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