SPIDER Circular Polarization Data Description

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CMB circular polarization results as discussed in Nagy et al. 2017 or (https://doi.org/10.3847/1538-4357/aa7cfd)

Mask: This is a FITS file containing the sky mask used in this analysis in equatorial coordinates with an Nside=512 pixelization. Roughly the region from 30 to 70 degrees in right ascension and -15 to -55 degrees in declination was used for this result.

CMB Power Spectrum: This text file contains the upper limits on CMB circular polarization presented in Figure 4 and Table 5 of Nagy et al. 2017. The first column lists the centers of the multipole bins, which have bin widths of 24. The second and third columns contain the 2-σ upper limits on l(l+1)C_lVV /(2π) in μK2_CMB at 95 and 150 GHz respectively. Note that due to the uncertainty in the circular polarization coupling of the half-wave plate polarization modulators, the multipole bins are highly correlated.

Extension to Other Sources: The limit above uses the temperature derivative of a CMB blackbody spectrum (dB/dT) for the source spectrum in the calculation of the circular polarization coupling parameters as described in Nagy et al. 2017. To extend this limit to other source spectra, we recompute the coupling parameters for several spectra of interest, and provide scale factors in this text file. The first column lists the functional form of the model, where v represents frequency. The second and third columns respectively contain the 95 and 150 GHz scale factors which should be multiplied by the the dB/dT limit (in μK2) at the relevant frequency.

The files are named as follows

  • Mask: Vmask.fits
  • CMB Power Spectrum: SPIDER_2sig_Vlimits.txt
  • Extension to Other Sources: SPIDER_limit_scaling.txt

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