Average fractional polarization of extragalactic sources at Planck frequencies
Journal
Date Issued
2018
Author(s)
Abstract
Recent detailed simulations have shown that an insufficiently accurate characterization of the contamination of unresolved polarized extragalactic sources can seriously bias measurements of the primordial cosmic microwave background (CMB) power spectrum if the tensor-to-scalar ratio r ∼ 0.001, as predicted by models currently of special interest (e.g., Starobinsky's R2 and Higgs inflation). This has motivated a reanalysis of the median polarization fraction of extragalactic sources (radio-loud AGNs and dusty galaxies) using data from the Planck polarization maps. Our approach, exploiting the intensity distribution analysis, mitigates or overcomes the most delicate aspects of earlier analyses based on stacking techniques. By means of simulations, we have shown that the residual noise bias on the median polarization fraction, Πmedian, of extragalactic sources is generally ≲0.1%. For radio sources, we have found Πmedian ≃ 2.83%, with no significant dependence on either frequency or flux density, in good agreement with the earlier estimate and with high-sensitivity measurements in the frequency range 5-40 GHz. No polarization signal is detected in the case of dusty galaxies, implying 90% confidence upper limits of Πdusty ≲ 2.2% at 353 GHz and of ≲3.9% at 217 GHz. The contamination of CMB polarization maps by unresolved point sources is discussed.
Volume
618
Start page
A29
Issn Identifier
0004-6361
Ads BibCode
2018A&A...618A..29T
Rights
open.access
File(s)![Thumbnail Image]()
![Thumbnail Image]()
Loading...
Name
1712.08412(2).pdf
Size
885.15 KB
Format
Adobe PDF
Checksum (MD5)
28d4ae8c9bd4c7325b8c76bce2c63a19
Loading...
Name
aa32342-17(1).pdf
Description
PDF editoriale
Size
860.11 KB
Format
Adobe PDF
Checksum (MD5)
1650b62b5122e26614b80139d40e5f1b