PLANCK REFERENCE SKY VERSUS WMAP DATA

cosmos.lbl.gov

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The aim of this work is to investigate the limitation and eventually possible improvement of Planck's Reference Sky.

The Planck Reference Sky consists in a simple model of the galactic foreground collected into a set of easy to use IDL routines, which can predict the sky brightness and polarization at any sky position and frequency.

The diffuse galactic components model currently includes 4 components which are calculated by distinct IDL functions: Free-Free, Synchrotron, Dust and eventually Spinning Dust. For more information on that click here

The compact sources components consist in the super position of three different templates: galaxy cluster, infrared sources and radio sources. For more information on that look at foregrounds page on cosmos

A better knowledge of foregrounds contamination will be the key factor to improve our knowledge about cmb; in fact the foreground contamination is estimated to be the main non-systematic sources of contamination for a cmb map. N. Ponthieu et al.

We can't suppress this contamination because we are embedded in these galactic and extragalactic emissions then we need to characterize foregrounds contamination to be able to discriminate between such mix of foreground incoming radiations and the CMB background. This estimation is very critical in polarization for the almost complete lack of data.

The Planck Reference Sky is probably the best that we can do with the available data but is still far to be enough. The main problem are:

lack of data close to the cosmological window

lack of data in polarization

The current philosophy for what concerns the first item is:

take the available survey (usually very far from the cosmological window)
rescale that with a rigid spectral index (usually obtained comparing two surveys or even patches of surveys in two different frequency close each others but far from the cosmological window)
use the original survey rescaled with the rigid spectral index like a template for foreground contamination into the cosmological window.

This is exactly the case of synchrotron radiation.In this case, for example, we can't forget that the physical mechanism are very different in the radio band and in the microwave. The amplitude and the morphology will be both completely different.

In polarization the situation is even worse. We used to "invent" everything: a polarization angle, a fraction of polarization sometimes having some clue sometimes unfortunately not.

The WMAP data and the incoming WMAP polarization data will offer a good opportunity to test the reliability of Planck's Reference Sky.

To take a look at the simulated maps and the WMAP maps, follow this link..

The first natural step will be test the power spectra of WMAP data versus the power spectra of Planck reference sky. If you are interested to the power spectra comparison follow this link..

Another interesting check is to test the spatial correlation; if you are interested on that follow this link..

Conclusion:

lack of power in the Planck Reference Sky ,even into the galactic plane particularly at lower frequency; this effect may came from a misestimation of free free or synchrotron template or from a missed component like Spinning Dust
the spatial correlation is in average around 0.8

If you need more detail please visit my web log here or feel free to send me an email .

Comments and suggestions are very welcome!