CMB Maps test

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NOTE: Text in red to be removed when filling the contents

Product description[edit]

A general description of the product, including e.g. figures related to the contents (e.g. maps, tables), and some explanation of its scientific meaning. If there are scientific warnings about the use of the product (User’s caveats), they should also be given here, or at least references to other explanatory documents (papers etc).

Three different estimates of the CMB are produced. The subsections below give a brief description of each method, and what are its advantages. Details of the motivations can be found in the corresponding paper #planck2013-06[06].

The CMB data are in thermodynamic temperature units (uK_cmb), and the residuals are in the units of the original sky map (K_cmb for the CMB channels, and MJy/sr for the Galactic channels). As usual, all maps are in Galactic coordinate and use Nested ordering scheme.


Cardoso to write brief intro with purpose, production method, inputs used, constraints


The aim of Sevem is to produce clean CMB maps at one or several frequencies by using a procedure based on template fitting. The templates are internal, i.e., they are constructed from Planck data, avoiding the need for external data sets, which usually complicates the analyses and may introduce inconsistencies. The method has been successfully applied to Planck simulations Leach et al., 2008 and to WMAP polarisation data Fernandez-cobos et al., 2012. In the cleaning process, no assumptions about the foregrounds or noise levels are needed, rendering the technique very robust.


Cardoso to write brief intro with purpose, production method, inputs used, constraints

Production process[edit]

Description of the Pipeline used to generate the product. In particular any limitations and approximations used in the data processing should be listed. Avoiding detailed descriptions of methods and referring to other parts of the ES and/or the relevant Planck papers for the details. References however should be quite detailed (i.e. it is not enough to direct the user to a paper, but the relevant section in the paper should be provided).


Cardoso to write brief intro with purpose, production method, inputs used, constraints


The templates are constructed by subtracting two neighbouring Planck frequency channel maps, after first smoothing them to a common resolution to ensure that the CMB signal is properly removed. A linear combination of the templates is then subtracted from the Planck sky map at the frequency to be cleaned, in order to produce the clean CMB. The coefficients of the linear combination are obtained by minimising the variance of the clean map outside a given mask. Although we exclude very contaminated regions during the minimization, the subtraction is performed for all pixels and, therefore, the cleaned maps cover the full-sky (although we expect that foreground residuals are present in the excluded areas).

An additional level of flexibility can also be considered: the linear coefficients can be the same for all the sky, or several regions with different sets of coefficients can be considered. The regions are then combined in a smooth way, by weighting the pixels at the boundaries, to avoid discontinuities in the clean maps. In order to take into account the different spectral behaviour of the foregrounds at low and high galactic latitudes, we have chosen to use two regions: the region with the 3 per cent brightest Galactic emission, and the region with the remaining 97 per cent of the sky.

Our final CMB map has then been constructed by combining the 143 and 217 GHz cleaned maps by weighting the maps in harmonic space taking into account the noise level, the resolution and a rough estimation of the foreground residuals of each map (obtained from realistic simulations). This final map has a resolution corresponding to a Gaussian beam of fwhm=5 arcminutes.



A list (and brief description to the extent possible) of the input data used to generate this product (down to file names), as well as any external ancillary data sets which were used.


Cardoso to write brief intro with purpose, production method, inputs used, constraints


The inputs maps used are all the Planck frequency channels. In particular, we have cleaned the 100, 143 GHz and 217 GHz maps using four templates constructed as the difference of the following Planck channels (smoothed to a common resolution): (30-44)GHz, (44-70)GHz, (545-353)GHz and (857-545)GHz. [from Laura Bonavera & Belen Barreiro, 18.feb.2013]


Related products[edit]

A description of other products that are related and share some commonalities with the product being described here. E.g. if the description is of a generic product (e.g. frequency maps), all the products falling into that type should be listed and referenced.

File names[edit]

The FITS files corresponding to the three CMB products are the following:

  • COM_CompMap_CMB-nilc_2048_R1.10.fits
  • COM_CompMap_CMB-sevem_2048_R1.10.fits
  • COM_CompMap_CMB-smica_2048_R1.10.fits

Meta Data[edit]

A detailed description of the data format of each file, including header keywords for fits files, extension names, column names, formats….

Each CMB products is delivered as a FITS file that contains four data extensions (nos. 1-4) in addition to a primary extension (no. 0) with no data. They contain:

Ext 1, 'COMP-MAP' : a CMB signal map accompanied by an uncertainty map, and two mask, all at Nside 2048. The CMB has been inpainted with likely values in regions where it could not be determined (namely over the Galactic Plane and some bright sources); the inpainted area covers ~3% of the sky. The uncertainty map is derived from the half-ring maps, which thus misses the low frequency components of the noise, but provides a reasonable estimate of the uncertainties at hi l, but not at low l, where residuals from the foregrounds become important. The masks are a validity mask to indicate where the resulting CMB is considered valid, and an inpainting mask to indicate where the CMB was inpainted.
Ext 2, 'FGDS-LFI' : foregrounds at the three LFI frequencies, at Nside 1024, built by smoothing the CMB map to the resolution of the given frequency
Ext 3, 'FGDS-HFI' : foregrounds at the six HFI frequencies, at Nside 2048, built by smoothing the CMB map to the resolution of the given frequency
Ext 4, 'BEAM-WF' : the beam transfer function, out to a value of ell that depends on the method and that is given in the header


<biblio force=false>

  1. References


Cosmic Microwave background

Flexible Image Transfer Specification

(Planck) Low Frequency Instrument

(Planck) High Frequency Instrument