CLASS 40 GHz 2016 - 2022 Observations (DR1)

Polarized Synchrotron Spectral Index Maps

Coordinate System:
Projection Type:
HEALPix, ring, Nside=32
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The polarized synchrotron spectral index (βs) is determined on 7° scales based on the linear correlation between Q and U maps for CLASS 40 GHz and WMAP K-band (23 GHz). Reobserved WMAP K-band data are used to mitigate the bias on βs introduced by the filtering applied in the CLASS 40 GHz mapmaking.

Prior to the βs computation, an estimate of the subdominant thermal dust emission is removed from the 40 GHz map. The 40 GHz dust contribution is computed assuming a modified black body spectrum characterized by a Q and U amplitude at 353 GHz (from reobserved Planck PR4 maps), a dust spectral index βd and a dust temperature Td. To assist in estimating the impact of the dust removal on βs, two different sets of dust spectral parameters were used: (1) a uniform βd = 1.53 and Td = 19.6 K, and (2) βd and Td that spatially vary as determined by the Planck 2015 Commander model.

Two files containing a βs map and its uncertainty are provided, corresponding to the choice of either the spatially uniform or varying dust model spectral parameters.

Additional Information:

CLASS Data Pipeline and Maps for 40 GHz Observations through 2022, Li et al. (2023)

CLASS Angular Power Spectra and Map-Component Analysis for 40 GHz Observations through 2022, Eimer et al. (2023)

A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Andrew F. Ptak
LAMBDA Director: Dr. Thomas M. Essinger-Hileman
NASA Official: Dr. Thomas M. Essinger-Hileman
Web Curator: Mr. Michael R. Greason