Open AccessB ‐mode contamination by synchrotron emission from 3‐yr Wilkinson Microwave Anisotropy Probe data
Author(s) -
Carretti E.,
Bernardi G.,
Cortiglioni S.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2006.00250.x
Subject(s) - cosmic microwave background , cmb cold spot , physics , astrophysics , sky , anisotropy , polarization (electrochemistry) , planck , synchrotron , microwave , cosmic background radiation , spectral index , galactic plane , spectral line , astronomy , optics , chemistry , galaxy , quantum mechanics
ABSTRACT We study the contamination of the B ‐mode of the cosmic microwave background polarization (CMBP) by Galactic synchrotron in the lowest emission regions of the sky. The 22.8‐GHz polarization map of the 3‐yr Wilkinson Microwave Anisotropy Probe ( WMAP ) data release is used to identify and analyse such regions. Two areas are selected with signal‐to‐noise ratio S/N < 2 and S/N < 3, covering ∼16 and ∼26 per cent fraction of the sky, respectively. The polarization power spectra of these two areas are dominated by the sky signal on large angular scales (multipoles ℓ < 15), while the noise prevails on degree scales. Angular extrapolations show that the synchrotron emission competes with the CMBP B ‐mode signal for tensor‐to‐scalar perturbation power ratio T / S = 10 −3 –10 −2 at 70 GHz in the 16 per cent lowest emission sky (S/N < 2 area). These values worsen by a factor ∼5 in the S/N < 3 region. The novelty is that our estimates regard the whole lowest emission regions and outline a contamination better than that of the whole high Galactic latitude sky found by the WMAP team ( T / S > 0.3) . Such regions allow T / S ∼ 10 −3 to be measured directly which approximately corresponds to the limit imposed by using a sky coverage of 15 per cent. This opens interesting perspectives on the investigation of the inflationary model space in lowest emission regions.