Some doubts on the validity of the foreground Galactic contribution subtraction from microwave anisotropies |
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Authors: | Martín López-Corredoira |
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Institution: | (1) Instituto de Astrofísica de Canarias, C/. Vía Láctea, s/n, E-38200 La Laguna (S/C de Tenerife), Spain |
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Abstract: | The Galactic foreground contamination in CMBR anisotropies, especially from the dust component, is not easily separable from
the cosmological or extragalactic component. In this paper, some doubts will be raised concerning the validity of the methods
used until now to remove Galactic dust emission and will show that none of them achieves its goal.
First, I review the recent bibliography on the topic and discuss critically the methods of foreground subtraction: the cross-correlation
with templates, analysis assuming the spectral shape of the Galactic components, the “maximum entropy method”, “internal linear
combination”, and “wavelet-based high resolution fitting of internal templates”. Second, I analyse the Galactic latitude dependence
from WMAP data. The frequency dependence is discussed with data in the available literature. The result is that all methods
of subtracting the Galactic contamination are inaccurate. The Galactic latitude dependence analysis or the frequency dependence
of the anisotropies in the range 50–250 GHz put a constraint on the maximum Galactic contribution in the power spectrum to
be less than ∼ 10% (68% C. L.) for an ∼ 1 degree scale, and possibly higher for larger scales.
The origin of most of the signals in the CMBR anisotropies is not Galactic. In any case, the subtraction of the galaxy is
not accurate enough to allow a “precision Cosmology”; other sources of contamination (extragalactic, solar system) are also
present. |
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Keywords: | Cosmic microwave background ISM: clouds dust extinction ISM: structure |
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