The Parkes Galactic Meridian Survey: observations and CMB polarization foreground analysis

Abstract

We present observations and cosmic microwave background (CMB) foreground analysis of the Parkes Galactic Meridian Survey, an investigation of the Galactic latitude behaviour of the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope. The survey consists of a 5 • wide strip along the Galactic meridian l = 254 • extending from the Galactic plane to the South Galactic pole. We identify three zones distinguished by polarized emission properties: the disc, the halo and a transition region connecting them. The halo section lies at latitudes |b| > 40 • and has weak and smooth polarized emission mostly at large scale with steep angular power spectra of median slope β med ∼ −2.6. The disc region covers the latitudes |b| < 20 • and has a brighter, more complex emission dominated by the small scales with flatter spectra of median slope β med = −1.8. The transition region has steep spectra as in the halo, but the emission increases towards the Galactic plane from halo to disc levels. The change of slope and emission structure at b ∼ −20 • is sudden, indicating a sharp disc-halo transition. The whole halo section is just one environment extended over 50 • with very low emission which, once scaled to 70 GHz, is equivalent to the CMB B-mode emission for a tensor-toscalar perturbation power ratio r halo = (3.3 ± 0.4) × 10 −3 . Applying a conservative cleaning procedure, we estimate an r detection limit of δr ∼ 2 × 10 −3 at 70 GHz (3σ confidence limit) and, assuming a dust polarization fraction of <12 per cent, δr ∼ 1 × 10 −2 at 150 GHz. The 150-GHz limit matches the goals of planned sub-orbital experiments, which can therefore be conducted at this high frequency. The 70-GHz limit is close to the goal of proposed next-generation space missions, which thus might not strictly require space-based platforms.

FIRST SEASON QUIET OBSERVATIONS: MEASUREMENTS OF COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRA AT 43 GHz IN THE MULTIPOLE RANGE 25 ⩽ $\ell$ ⩽ 475

“…No significant power is found in any other case. The non-detection of foreground power at > 75 is consistent with the expected foreground dependence: ∝ −2.5 (Carretti et al 2010), and the low power found inĈ KK b=1 . The excess power observed in the first EE bin of CMB-1 is fully consistent with a typical synchrotron frequency spectrum.…”

Power Spectrum Analysis of Polarized Emission From the Canadian Galactic Plane Survey

“…The power decreases as a power law from the smallest sampled multipole to ∼ 10 3 . If we consider the trend in this portion of the plot as a simple power law of the form P( ) ∝ −α , the index α is usually reported in similar studies e.g., Haverkorn et al (2003), Giardino et al (2002), Carretti et al (2010). Other structures in the power spectra are not universally seen, though Haverkorn et al (2003) and Carretti et al (2010) do mention a flattening at high multipoles due to noise in the image.…”

“…In this paper we take a third approach, using statistical methods to examine the spatial scales of polarization structures. Such analysis has been done before with focus on calculating the angular power spectra or the structure functions of the polarized emission (Tucci et al 2000;Giardino et al 2001;Tucci et al 2002;Bruscoli et al 2002;Giardino et al 2002;Haverkorn et al 2003Haverkorn et al , 2004Haverkorn et al , 2006Haverkorn et al , 2008La Porta & Burigana 2006;Carretti et al 2005Carretti et al , 2010 . More recently, the work of Gaensler et al (2011) demonstrated that the statistics of the gradient of polarized emission provided clear measurements of the magnetoionic medium.…”

A new perspective on turbulent Galactic magnetic fields through comparison of linear polarization decomposition techniques

“…S-PASS is a single-dish polarimetric survey of the entire southern sky at 2.3 GHz, performed with the Parkes 64 m Radio Telescope and its S-band receiver with beam width FWHM=8.9 arcmin (Carretti et al, in prep. and Carretti et al (2013), see also Carretti et al (2010) and Iacobelli et al (2014)). Final maps were convolved with a Gaussian window of FWHM = 6 arcmin to a final resolution of 10.75 arcmin.…”

“…As noticed by Robitaille & Scaife (2015), the wavelet power spectra do not sample properly the drop of power caused by the telescope beam. Thus, in order to measure power laws corrected for the effective beam, Fourier power spectra have been fitted with a similar relation to that of Carretti et al (2010) :…”