The impact of Galactic synchrotron emission  
 on CMB anisotropy measurements

Porta, L. La; Burigana, C.; Reich, W.; Reich, P.

doi:10.1051/0004-6361:20078435

Cited by 69 publications

(83 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The slope is within the range of slopes [-2, -3] found by all the previous measurements at higher frequencies (Tegmark & Efstathiou 1996;Giardino et al 2001;Bennett et al 2003;La Porta et al 2008).…”

Section: Power Spectrum Analysissupporting

confidence: 83%

“…At large angular scales there is a power-law behaviour, with power decreasing at increasing angular scale. This behaviour is typical of the Galactic diffuse emission observed at higher frequencies and higher angular resolutions (Bennett et al 2003;La Porta et al 2008).…”

Section: Power Spectrum Analysissupporting

confidence: 56%

“…La Porta et al (2008) analysed power spectra of the diffuse Galactic synchrotron radiation down to scales of a few degrees and found significant variations across the sky even after subtracting the brightest sources.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Foregrounds for observations of the cosmological 21 cm line

Bernardi¹,

Bruyn

Brentjens

et al. 2009

A&A

196

230

View full text Add to dashboard Cite

Context. The cosmological 21 cm line promises to be a formidable tool for cosmology, allowing the investigation of the end of the so-called dark ages, when the first galaxies formed. Aims. Astrophysical foregrounds are expected to be about three orders of magnitude greater than the cosmological signal and therefore represent a serious contamination of the cosmological 21 cm line. Detailed knowledge of both their intensity and polarization structure on the relevant angular scale of 1-30 arcmin will be essential for extracting the cosmological signal from the data. Methods. We present the first results from a series of observations conducted with the Westerbork telescope in the 140-160 MHz range with a 2 arcmin resolution aimed at characterizing the properties of the foregrounds for epoch of reionization experiments. The polarization data were analysed through the rotation measure synthesis technique. We computed total intensity and polarization angular power spectra. Results. For the first time we have detected fluctuations in the Galactic diffuse emission on scales greater than 13 arcmin at 150 MHz, in the low Galactic latitude area known as Fan region, centred at α = 3 h 10 m , δ = 65 • 30 . Those fluctuations have an rms of 14 K. The total intensity power spectrum shows a power-law behaviour down to ∼900 with slope β I = −2.2 ± 0.3. The detection of diffuse emission at smaller angular scales is limited by residual point sources. We measured an rms confusion noise of ∼3 mJy beam −1 . Diffuse polarized emission was also detected for the first time at this frequency. The polarized signal shows complex structure both spatially and along the line of sight. The polarization power spectrum is not affected by residual point sources and is only limited by the thermal noise. It shows a power-law behaviour down to ∼2700 with slope β P = −1.65±0.15. The rms of polarization fluctuations is 7.2 K on 4 arcmin scales. Conclusions. The measured total intensity fluctuations are used to estimate the foreground contamination on the cosmological signal.By extrapolating the spectrum of total intensity emission, we find a contamination of δT = ( + 1)C I /2π ∼ 5.7 K on 5 arcmin scales and a corresponding rms value of ∼18.3 K at the same angular scale. The level of the polarization power spectrum is δT ∼ 3.3 K on 5 arcmin scales. However, the Fan region cannot be taken as representative of other sky regions, given its exceptionally bright polarized signal, but is likely to represent an upper limit on the sky brightness at moderate and high Galactic latitude.

show abstract

Section: Power Spectrum Analysissupporting

confidence: 83%

Section: Power Spectrum Analysissupporting

confidence: 56%

See 1 more Smart Citation

Foregrounds for observations of the cosmological 21 cm line

Bernardi¹,

Bruyn

Brentjens

et al. 2009

A&A

196

230

View full text Add to dashboard Cite

show abstract

“…The analysis of synchrotron fluctuations deals with magnetic fluctuations, and previous studies of the angular power spectrum of the Galactic radio diffuse synchrotron emission (see e.g. Giardino et al 2001;La Porta et al 2008) have shown it can be fitted by a power law, C l ∝ l α , with α ∼ [−3.0, −2.5] and l 200. Moreover, strong local variations in the index exist.…”

Section: Discussionmentioning

confidence: 99%

Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

Iacobelli

Haverkorn

Orrù

et al. 2013

A&A

Self Cite

View full text Add to dashboard Cite

Aims. The characteristic outer scale of turbulence (i.e. the scale at which the dominant source of turbulence injects energy to the interstellar medium) and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters. Methods. We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l, b) ∼ (137.0 • , +7.0 • ) at 80 × 70 resolution in the range [146, 174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations. Results. We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum displays a power law behaviour for scales between 100 and 8 arcmin with a slope α = −1.84 ± 0.19. We find an upper limit of ∼20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region, which is in agreement with previous estimates in literature. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes. Conclusions. We present the first LOFAR detection and imaging of the Galactic diffuse synchrotron emission around 160 MHz from the highly polarized Fan region. The power spectrum of the foreground synchrotron fluctuations is approximately a power law with a slope α ≈ −1.84 up to angular multipoles of 1300, corresponding to an angular scale of ∼8 arcmin. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence (L out ) of the Galactic synchrotron foreground, finding a range of plausible values of 10−20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates.

show abstract

“…Radio frequency information such as the Leiden 408 MHz and 1.4 GHz surveys (Brouw & Spoelstra 1976;Wolleben et al 2006), the Parkes survey at 2.4 GHz (Duncan et al 1999), and the MGLS survey (Medium Galactic Latitude Survey) at 1.4 GHz (Uyaniker et al 1999) are generally used to provide insight the Galactic diffuse synchrotron emission in polarized intensity. However, Faraday rotation introduces complications into the interpretation of such data since strong depolarization is expected for frequencies lower than 10 GHz (Burn 1966;Sun et al 2008;Jaffe et al 2010;Jansson et al 2009;La Porta et al 2008, 2006. Consequently, the best polarized Galactic diffuse synchrotron tracers are at high frequency such as the Wmap survey at 23 GHz (Page et al 2007).…”

Section: Diffuse Galactic Synchrotron Emissionmentioning

confidence: 99%

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

Fauvet

Macías-Pérez

Aumont

et al. 2011

A&A

View full text Add to dashboard Cite

Aims. We present for the first time a coherent model of the polarized Galactic synchrotron and thermal dust emissions that are likely to form the predominant diffuse foregrounds for measuring the polarized CMB fluctuations by the Planck satellite mission. Methods. We produced 3D models of the Galactic magnetic field including regular and turbulent components, and of the distribution of matter in the Galaxy including relativistic electron and dust grain components. By integrating along the line of sight, we constructed maps of the polarized Galactic synchrotron and thermal dust emission for each of these models and compared them to currently available data. We consider the 408 MHz all-sky continuum survey, the 23 GHz band of the Wilkinson Microwave Anisotropy Probe, and the 353 GHz Archeops data. Results. The best-fit parameters obtained are consistent with previous estimates in the literature based only on synchrotron emission and pulsar rotation measurements and this allows us to reproduce the large-scale features observed in the data. Unmodeled local Galactic structures and the effect of turbulence make it difficult to accurately reconstruct observations in the Galactic plane. Conclusions. Finally, using the best-fit model we are able to estimate the expected polarized foreground contamination at the Planck frequency bands. For the CMB bands, 70, 100, 143 and 217 GHz, at high Galactic latitudes although the CMB signal dominates in general, a significant foreground contribution is expected at large angular scales. In particular, this contribution will dominate the CMB signal for the B modes expected from realistic models of a background of primordial gravitational waves.

show abstract

The impact of Galactic synchrotron emission on CMB anisotropy measurements

Cited by 69 publications

References 50 publications

Foregrounds for observations of the cosmological 21 cm line

Foregrounds for observations of the cosmological 21 cm line

Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

Contact Info

Product

Resources

About