Full sky study of diffuse Galactic emission   at decimeter 
wavelenghts

Platania, P.; Burigana, C.; Maino, D.; Caserini, E.; Bersanelli, M.; Cappellini, B.; Mennella, A.

doi:10.1051/0004-6361:20031125

Cited by 88 publications

(112 citation statements)

References 12 publications

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“…4 implies that the halo is still present in the unpolarized cm-wavelength maps, because the data are well-fitted with our synchrotron model, which has a constant shape, so that the synchrotron distribution is no different at 20 or 30 GHz from 408 MHz. Although, as we have seen, this separation is subject to substantial uncertainties, it is corroborated by spectral analysis of ground-based surveys (Reich & Reich 1988;Platania et al 2003) that find that the halo and spurs have similar spectral indices near 1 GHz.…”

Section: Overview Of Polarized Synchrotron Emissionsupporting

confidence: 75%

Planck2015 results

Ade

Aghanim

Alves

et al. 2016

A&A

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165

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We discuss the Galactic foreground emission between 20 and 100 GHz based on observations by Planck and WMAP. The total intensity in this part of the spectrum is dominated by free-free and spinning dust emission, whereas the polarized intensity is dominated by synchrotron emission. The Commander component-separation tool has been used to separate the various astrophysical processes in total intensity. Comparison with radio recombination line templates verifies the recovery of the free-free emission along the Galactic plane. Comparison of the high-latitude Hα emission with our free-free map shows residuals that correlate with dust optical depth, consistent with a fraction (≈30%) of Hα having been scattered by high-latitude dust. We highlight a number of diffuse spinning dust morphological features at high latitude. There is substantial spatial variation in the spinning dust spectrum, with the emission peak (in I ν ) ranging from below 20 GHz to more than 50 GHz. There is a strong tendency for the spinning dust component near many prominent H ii regions to have a higher peak frequency, suggesting that this increase in peak frequency is associated with dust in the photo-dissociation regions around the nebulae. The emissivity of spinning dust in these diffuse regions is of the same order as previous detections in the literature. Over the entire sky, the Commander solution finds more anomalous microwave emission (AME) than the WMAP component maps, at the expense of synchrotron and free-free emission. This can be explained by the difficulty in separating multiple broadband components with a limited number of frequency maps. Future surveys, particularly at 5-20 GHz, will greatly improve the separation by constraining the synchrotron spectrum. We combine Planck and WMAP data to make the highest signal-to-noise ratio maps yet of the intensity of the all-sky polarized synchrotron emission at frequencies above a few GHz. Most of the high-latitude polarized emission is associated with distinct large-scale loops and spurs, and we re-discuss their structure. We argue that nearly all the emission at 40 • > l > −90 • is part of the Loop I structure, and show that the emission extends much further in to the southern Galactic hemisphere than previously recognised, giving Loop I an ovoid rather than circular outline. However, it does not continue as far as the "Fermi bubble/microwave haze", making it less probable that these are part of the same structure. We identify a number of new faint features in the polarized sky, including a dearth of polarized synchrotron emission directly correlated with a narrow, roughly 20 • long filament seen in Hα at high Galactic latitude. Finally, we look for evidence of polarized AME, however many AME regions are significantly contaminated by polarized synchrotron emission, and we find a 2σ upper limit of 1.6% in the Perseus region.

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Section: Overview Of Polarized Synchrotron Emissionsupporting

confidence: 75%

Planck2015 results

Ade

Aghanim

Alves

et al. 2016

A&A

Self Cite

165

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“…"Stripes" are systematic baseline distortions in the telescope's scanning direction and are mainly due to the limited stability of the receiving system and to the influence of weather conditions. They could also be cancelled from the list of possible causes from the comparison with a destriped version of the 408 MHz map (Platania et al 2003). The cut-off APS of the two versions of the 408 MHz map present only marginal differences at intermediate multipoles (see Fig.…”

Section: The Aps Of Large Areas: Analysis For Various Cutsmentioning

confidence: 99%

The impact of Galactic synchrotron emission on CMB anisotropy measurements

Porta¹,

Burigana

Reich³

et al. 2007

A&A

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Context. Galactic foreground emission fluctuations are a limiting factor for precise cosmic microwave background (CMB) anisotropy measurements. Aims. We intend to improve current estimates of the influence of Galactic synchrotron emission on the analysis of CMB anisotropies. Methods. We perform an angular power spectrum analysis (APS) of all-sky total intensity maps at 408 MHz and 1420 MHz, which are dominated by synchrotron emission out of the Galactic plane. We subtract the brighter sources from the maps, which turns out to be essential for the results obtained. We study the APS as a function of Galactic latitude by considering various cuts and as a function of sky position by dividing the sky into patches of ∼15• × 15 • in size. Results. The APS of the Galactic radio diffuse synchrotron emission is best fitted by a power law, C ∼ k α , with α ∈ [−3.0, −2.6], where the lower values of α typically correspond to the higher latitudes. Nevertheless, the analysis of the patches reveals that strong local variations exist. A good correlation is found between the APS normalized amplitude, k 100 = k×100 α , at 408 MHz and 1420 MHz. The mean APS for ∈ [20, 40] is used to determine the mean spectral index between 408 MHz and 1420 MHz, β (0.408−1.4) GHz ∈ [−3.2, −2.9] (C (ν) ∝ ν −2β ), which is then adopted to extrapolate the synchrotron APS results to the microwave range. Conclusions. We use the 408 MHz and 1420 MHz APS results to predict the Galactic synchrotron emission fluctuations at frequencies above 20 GHz. A simple extrapolation to 23 GHz of the synchrotron emission APS found at these radio frequencies does not explain all the power in the WMAP synchrotron component even at middle/high Galactic latitudes. This suggests a significant microwave contribution (of about 50% of the signal) by other components such as free-free or spinning dust emission. The comparison between the extrapolated synchrotron APS and the CMB APS shows that a mask excluding the regions with |b gal | < ∼ 5• would reduce the foreground fluctuations to about half of the cosmological ones at 70 GHz even at the lowest multipoles. The main implications of our analysis for the cosmological exploitation of microwave temperature anisotropy maps are discussed.

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“…Modeling of Galactic CR emissivity by Beuermann et al (1985) based on the all-sky 408 MHz single-dish maps of Haslam et al (1982) derive a typical CR emissivity of $10 K kpc À1 at 408 MHz. Platania et al (2003) examine the temperature spectral index of Galactic nonthermal emission through a comparison of the Haslam et al (1982) 408 MHz map and the 1400 MHz map of Reich (1982) and arrive at T ( ) / À2:7 . With these values, the expected emissivity at 74 MHz may be estimated.…”

Section: Deriving Cosmic-ray Emissivity Behindmentioning

confidence: 99%

74 MHz Discrete HiiAbsorption Regions Toward the Inner Galaxy

et al. 2006

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At low radio frequencies ( P 100 MHz), classical H ii regions may become optically thick (optical depth ! 1) and can be observed as discrete absorption regions against the Galactic nonthermal background emission created by Galactic cosmic-ray electrons spiraling around magnetic fields. However, the historically poor angular resolution (>30 0 ) of previous low-frequency surveys has limited such observations to the largest and nearest H ii regions. The significantly enhanced resolution and surface brightness sensitivity of the 74 MHz system on the Very Large Array now allow for the detection of absorption regions on scale sizes of just a few arcminutes that can be readily identified with many more H ii regions previously cataloged in emission at higher frequencies. These absorption measurements directly constrain the brightness temperature of the cosmic-ray synchrotron emission emanating from behind the H ii regions based on reasonable physical assumptions. Many such observations could be used to map out the threedimensional cosmic-ray emissivity in the Galaxy without resorting to a priori assumptions about Galactic structure. This measurement is unique to low-frequency radio astronomy. In this work we present 74 MHz observations in the region 26 > l > À15 , À5 < b < 5 ; report the detection of 92 absorption features associated with known H ii regions; and derive the brightness temperature of the Galactic cosmic-ray electron synchrotron emission emanating from the column behind these regions. For the 42 H ii regions with known distances, the average emissivity of the column behind the H ii region is derived. The 74 MHz emissivity values range between 0.3 and 1.0 K pc À1 for a model assuming uniform distribution of emissivity. Methods for using this type of data to model the three-dimensional distribution of cosmic-ray emissivity and the possibility of using this method to break the H ii region kinematic distance degeneracy are discussed.

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Full sky study of diffuse Galactic emission at decimeter wavelenghts

Cited by 88 publications

References 12 publications

Planck2015 results

Planck2015 results

The impact of Galactic synchrotron emission on CMB anisotropy measurements

74 MHz Discrete HiiAbsorption Regions Toward the Inner Galaxy

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