High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

Details High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

2004-12-22

arxiv.org/abs/astro-ph/0412598v1

Mon.Not.Roy.Astron.Soc. 358 (2005) 1-12

Astronomy and Astrophysics

Astrophysics

13 pages, 11 figures, accepted for publication in MNRAS

Scientific paper

10.1111/j.1365-2966.2005.08761.x

We analyse the polarized emission at 1.4 GHz in a 3x3 deg^2 area at high Galactic latitude (b ~ -40deg). The region, centred in (RA=5h, Dec=-49deg), was observed with the Australia Telescope Compact Array radio-interferometer, whose 3-30 arcmin angular sensitivity range allows the study of scales appropriate for CMB Polarization (CMBP) investigations. The angular behavior of the diffuse emission is analysed through the E- and B-mode power spectra. These follow a power law $C^X_l \propto l^{\beta_X}$ with slopes \beta_E = -1.97 \pm 0.08 and \beta_B = -1.98 \pm 0.07. The emission is found to be about a factor 25 fainter than in Galactic plane regions. The comparison of the power spectra with other surveys indicates that this area is intermediate between strong and negligible Faraday rotation effects. A similar conclusion can be reached by analysing both the frequency and Galactic latitude behaviors of the diffuse Galactic emission of the 408-1411 MHz Leiden survey data. We present an analysis of the Faraday rotation effects on the polarized power spectra, and find that the observed power spectra can be enhanced by a transfer of power from large to small angular scales. The extrapolation of the spectra to 32 and 90GHz of the CMB window suggests that Galactic synchrotron emission leaves the CMBP E-mode uncontaminated at 32GHz. The level of the contamination at 90GHz is expected to be more than 4 orders of magnitude below the CMBP spectrum. Extrapolating to the relevant angular scales, this region also appears adequate for investigation of the CMBP B-modes for models with tensor/scalar fluctuation power ratio T/S>0.01. We also identify polarized point sources in the field, providing a 9 object list which is complete down to the polarized flux limit of S^p_lim = 2 mJy.

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