Constraining topological defects with temperature and polarization anisotropies

Abstract

We analyse the possible contribution of topological defects to cosmic microwave anisotropies, both temperature and polarisation. We allow for the presence of both inflationary scalars and tensors, and of polarised dust foregrounds that may contribute to or dominate the B-mode polarisation signal. We confirm and quantify our previous statements that topological defects on their own are a poor fit to the B-mode signal. However, adding topological defects to a models with a tensor component or a dust component improves the fit around $\ell =200$. Fitting simultaneously to both temperature and polarisation data, we find that textures fit almost as well as tensors ($\Delta {\chi }^2=2.0$), while Abelian Higgs strings are ruled out as the sole source of the B-mode signal at low $\ell$. The 95% confidence upper limits on models combining defects and dust are $G\mu <2.7\times 10^{-7}$ (Abelian Higgs strings), $G\mu <9.8\times 10^{-7}$ (semilocal strings) and $G\mu <7.3\times 10^{-7}$ (textures), a small reduction on the $Planck$ bounds. The most economical fit overall is obtained by the standard $\Lambda$CDM model with a polarised dust component.

8 pages, 3 figures. Temperature and polarization anisotropy power spectra for Abelian Higgs strings, semilocal strings and textures are included as ancillary files. Minor changes, matches published version

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• How to simulate global cosmic strings with large string tension
• Constraints on the Nambu-Goto cosmic string contribution to the CMB power spectrum in light of new temperature and polarisation data
• Observational Constraints on Varying-alpha Domain Walls
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