HEALPix maps

CONDITIONS FOR USING S-PASS DATA

You are welcome to use the S-PASS data, but we request that:

if you use these data in your work you cite the paper describing the survey: Carretti E, Haverkorn M, Staveley-Smith L, Bernardi G, Gaensler B M, Kesteven M, Poppi S, Brown S, Crocker R, Purcell C R, Schnitzeler D, Sun X, 2019, MNRAS, 489, 2330
In the acknowledgements section of your work you add the following: This work has made use of S-band Polarisation All Sky Survey (S-PASS) data.

HEALPix Maps

Stokes Q: spass_dr1_1902_healpix_Tb.q.fit
Stokes U: spass_dr1_1902_healpix_Tb.u.fits
Stokes I: spass_dr1_1902_healpix_Tb.i.fits
Sensitivity (Q & U): spass_dr1_1902_healpix_Tb_sens.fits
RM: RM map
RM error: RM error map

IMPORTANT WARNING

S-PASS follows the IAU convention on Polarisation Angles (PA), as most of astrophysical data.

That means PA is 0 northward (of the coordinate system used) and increases eastward.

This is the IAU standard and if you use a standard astronomical FITS image you should be right.

However, we are aware that there are a few data sets and softwares that use a different convention, with PA increasing westward. Examples of popular data sets doing so are WMAP and Planck data, and the HEALPix software package. Passing from one system to the other means simply to change sign of Stokes U (or sign of the PA).

To reflect this the S-PASS healpix fits file header contains the keyword POLCCONV = 'IAU'.

We suggest to bear this in mind when using S-PASS (and most of astrophysical data sets) in combination with WMAP and Planck data (and possibly other CMB data sets) or with the HEALPix package.

Report abuse