Cross-correlation Analysis of the SPIDER Experiment

Abstract

The B-mode polarization in the cosmic microwave background (CMB) radiation has been actively searched for in recent CMB experiments. Since the signal, if exists, is expected to be very faint, the studies of polarized forgrounds have become necessary. We use data from SPIDER and Planck to characterize polarized dust emission and Galactic synchrotron radiation. Using two frequency channels from SPIDER (90, 150 GHz) and four from Planck (100, 143, 217, 353 GHz), we generate all possible EE and BB cross-power spectra. Within each multipole bin, we fit two frequencies models to the data, with and without contribution from synchrotron. We present the fitted parameters. We find that the mean dust spectral indices for EE and BB are statistically different. Without synchrotron contribution, we estimate that β EE d = 1.45+0.06 −0.06 and β BB d = 1.62+0.10 −0.09. With synchotron contribution, we find β EE d = 1.37+0.06 −0.07 and β BB d = 1.56+0.09 −0.08. However, if we truncate our analysis up to the multipole l ∼ 145, the differences between the two shrink. β EE d and β BB d are within uncertainties, and the estimated values approach what reported in Planck Collaboration Int. LIV. This suggests that the physical properties of dust depend on angular scale. We also investigate the impacts of using actual band centers estimated by flat spectrum source, instead of using the nominal band centers. We find that the values of the fitted parameters are 6% differences for the CMB amplitude and the dust spectral index and are 18% differences for the dust amplitude.