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Title: Fractional Polarisation of Extragalactic Sources in the 500-square-degree SPTpol Survey

Abstract

We study the polarisation properties of extragalactic sources at 95 and 150 GHz in the SPTpol 500 deg$^2$ survey. We estimate the polarised power by stacking maps at known source positions, and correct for noise bias by subtracting the mean polarised power at random positions in the maps. We show that the method is unbiased using a set of simulated maps with similar noise properties to the real SPTpol maps. We find a flux-weighted mean-squared polarisation fraction $$\langle p^2 \rangle= [8.9\pm1.1] \times 10^{-4}$$ at 95 GHz and $$[6.9\pm1.1] \times 10^{-4}$$ at 150~GHz for the full sample. This is consistent with the values obtained for a sub-sample of active galactic nuclei. For dusty sources, we find 95 per cent upper limits of $$\langle p^2 \rangle_{\rm 95}<16.9 \times 10^{-3}$$ and $$\langle p^2 \rangle_{\rm 150}<2.6 \times 10^{-3}$$. We find no evidence that the polarisation fraction depends on the source flux or observing frequency. The 1-$$\sigma$$ upper limit on measured mean squared polarisation fraction at 150 GHz implies that extragalactic foregrounds will be subdominant to the CMB E and B mode polarisation power spectra out to at least $$\ell\lesssim5700$$ ($$\ell\lesssim4700$$) and $$\ell\lesssim5300$$ ($$\ell\lesssim3600$$), respectively at 95 (150) GHz.

Authors:
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
SPT
OSTI Identifier:
1556975
Report Number(s):
FERMILAB-PUB-19-386-AE; arXiv:1907.02156
1742660
DOE Contract Number:  
AC02-07CH11359
Resource Type:
Journal Article
Journal Name:
TBD
Additional Journal Information:
Journal Name: TBD
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Gupta, N., and et al. Fractional Polarisation of Extragalactic Sources in the 500-square-degree SPTpol Survey. United States: N. p., 2019. Web.
Gupta, N., & et al. Fractional Polarisation of Extragalactic Sources in the 500-square-degree SPTpol Survey. United States.
Gupta, N., and et al. Wed . "Fractional Polarisation of Extragalactic Sources in the 500-square-degree SPTpol Survey". United States. https://www.osti.gov/servlets/purl/1556975.
@article{osti_1556975,
title = {Fractional Polarisation of Extragalactic Sources in the 500-square-degree SPTpol Survey},
author = {Gupta, N. and et al.},
abstractNote = {We study the polarisation properties of extragalactic sources at 95 and 150 GHz in the SPTpol 500 deg$^2$ survey. We estimate the polarised power by stacking maps at known source positions, and correct for noise bias by subtracting the mean polarised power at random positions in the maps. We show that the method is unbiased using a set of simulated maps with similar noise properties to the real SPTpol maps. We find a flux-weighted mean-squared polarisation fraction $\langle p^2 \rangle= [8.9\pm1.1] \times 10^{-4}$ at 95 GHz and $[6.9\pm1.1] \times 10^{-4}$ at 150~GHz for the full sample. This is consistent with the values obtained for a sub-sample of active galactic nuclei. For dusty sources, we find 95 per cent upper limits of $\langle p^2 \rangle_{\rm 95}<16.9 \times 10^{-3}$ and $\langle p^2 \rangle_{\rm 150}<2.6 \times 10^{-3}$. We find no evidence that the polarisation fraction depends on the source flux or observing frequency. The 1-$\sigma$ upper limit on measured mean squared polarisation fraction at 150 GHz implies that extragalactic foregrounds will be subdominant to the CMB E and B mode polarisation power spectra out to at least $\ell\lesssim5700$ ($\ell\lesssim4700$) and $\ell\lesssim5300$ ($\ell\lesssim3600$), respectively at 95 (150) GHz.},
doi = {},
journal = {TBD},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {7}
}