C.D.S. - SIMBAD4 rel 1.7 - 2019.11.15CET12:32:08

2018A&A...618A.166K - Astronomy and Astrophysics, volume 618A, 166-166 (2018/1-0)

S-PASS view of polarized Galactic synchrotron at 2.3 GHz as a contaminant to CMB observations.


Abstract (from CDS):

We have analyzed the southern sky emission in linear polarization at 2.3 GHz as observed by the S -band Polarization All Sky Survey (S-PASS). Our purpose is to study the properties of the diffuse Galactic polarized synchrotron as a contaminant to B-mode observations of the cosmic microwave background (CMB) polarization. We studied the angular distribution of the S-PASS signal at intermediate and high Galactic latitudes by means of the polarization angular power spectra. The power spectra, computed in the multipole interval 20≤l≤1000, show a decay of the spectral amplitude as a function of multipole for l≤200, typical of the diffuse emission. At smaller angular scales, power spectra are dominated by the radio point source radiation. We find that, at low multipoles, spectra can be approximated by a power law ClEE,BB∝lα, with α~=-3, and characterized by a B-to-E ratio of about 0.5. We measured the polarized synchrotron spectral energy distribution (SED) in harmonic space, by combining S-PASS power spectra with low frequency WMAP and Planck ones, and by fitting their frequency dependence in six multipole bins, in the range 20≤l≤140. Results show that the recovered SED, in the frequency range 2.3-33GHz, is compatible with a power law with βs=-3.22±0.08, which appears to be constant over the considered multipole range and in the different Galactic cuts. Combining the S-PASS total polarized intensity maps with those coming from WMAP and Planck we derived a map of the synchrotron spectral index βs at angular resolution of 2° on about 30% of the sky. The recovered βs distribution peaks at the value around -3.2. It exibits an angular power spectrum which can be approximated with a power law Cl∝lγ with γ~=-2.6. We also measured a significant spatial correlation between synchrotron and thermal dust signals, as traced by the Planck 353GHz channel. This correlation reaches about 40% on the larger angular scales, decaying considerably at the degree scales. Finally, we used the S-PASS maps to assess the polarized synchrotron contamination to CMB observations of the B-modes at higher frequencies. We divided the sky in small patches (with fsky~=1%) and find that, at 90GHz, the minimal contamination, in the cleanest regions of the sky, is at the level of an equivalent tensor-to-scalar ratio rsynch~=10–3. Moreover, by combining S-PASS data with Planck 353GHz observations, we recover a map of the minimum level of total polarized foreground contamination to B-modes, finding that there is no region of the sky, at any frequency, where this contamination lies below equivalent tenor-to-scalar ratio rFG~=10–3. This result confirms the importance of observing both high and low frequency foregrounds in CMB B-mode measurements.

Abstract Copyright: © ESO 2018

Journal keyword(s): polarization - methods: data analysis - Galaxy: general - cosmic background radiation - diffuse radiation - radio continuum: ISM

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 2MASX J00461775-4207512 AGN 00 46 17.760 -42 07 51.29   17   15.78   ~ 75 1
2 NAME SGP reg 00 51 26.275 -27 07 41.70           ~ 498 0
3 NGC 1316 GiP 03 22 41.789 -37 12 29.52 9.81 9.15 8.53 7.66   ~ 1163 1
4 QSO B0407-65 QSO 04 08 20.37884 -65 45 09.0806     18.0     ~ 95 1
5 ICRF J052109.8+163822 Sy1 05 21 09.88592749 +16 38 22.0517668   19.37 18.84 18.480   ~ 726 1
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14348 1
7 NAME Centaurus A Sy2 13 25 27.61509104 -43 01 08.8056025   8.18 6.84 6.66   ~ 3896 3
8 ICRF J193925.0-634245 Sy2 19 39 25.02671 -63 42 45.6255   18.87 18.37 17.64   ~ 921 1

    Equat.    Gal    SGal    Ecl

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