The second part of this section is mostly unreadable. Please use proper style in terms of sectioning (i.e. pseudo headings that are underlined), lists (bullet or numbered) - see other pages for examples. Info regarding M3 (and NERCS) is probably irrelevant to external users)
The effective beam is the average of all scanning beams pointing at a certain direction within a given pixel of the sky map for a given scan strategy. It takes into account the coupling between azimuthal asymmetry of the beam and the uneven distribution of scanning angles across the sky. It captures the complete information about the difference between the true and observed image of the sky. They are, by definition, the objects whose convolution with the true CMB sky produce the observed sky map.
The effective beam is computed by stacking within a small field around each pixel of the HEALPix sky map. Due to the particular features of Planck scanning strategy coupled to the beam asymmetries in the focal plane, and data processing of the bolometer and radiometer TOIs, the resulting Planck effective beams vary over the sky.
- Comparison of the images of compact sources observed by Planck-HFI with the results of FEBeCoP
We show here a comparison of the FEBeCoP derived effective beams, and associated point spread functions (see here), to the actual images of a few compact sources observed by Planck, for 30GHz and 100GHz frequency channels. We show below a few panels of source images organized as follows:
- Row #1- DX9 images of four ERCSC objects with their galactic (l,b) coordinates shown under the color bar
- Row #2- linear scale FEBeCoP PSFs computed using input scanning beams BS Mars12 apodized for the CMB channels and the BS Mars12 for the sub-mm channels
- Row #3- log scale of #2; PSF iso-contours shown in solid line, elliptical Gaussian fit iso-contours shown in broken line
- 30 GHz and 100 GHz
- Statistics of the effective beams computed using FEBeCoP for 100-857 GHz channels
We tabulate the simple statistics of FWHM, ellipticity, orientation and beam solid angle for a sample of 3072 directions mentioned above. Statistics shown in the Table are derived from the histograms shown above.
- The results/table for delivery for the Cosmo-channels (100 to 353GHz) were obtained with the v53 BS Mars12_apodized beam maps recently provided.
- We also provide the beam derived parameters for GH Mars12 for the cosmology channels (which do not suffer from convergence issues).
|Column Name||Data Type||Units||Description|
|I_stdev||Real*4||MJy/sr||standard deviation of intensity|
|Em_stdev||Real*4||standard deviation on emissivity|
|T_stdev||Real*4||uK||standard deviation on temerature|
|frequency||mean(fwhm)[[<<]][arcmin]||sd(fwhm)[[<<]][arcmin]||mean(e)||sd(e)||mean(psi)[[<<]][degree]||sd(psi)[[<<]][degree]||mean(Solid Angle)[[<<]][arcmin'^2^']||sd(Solid Angle)[[<<]][arcmin'^2^']||100||9.651||0.014||1.186||0.023||-0.024||55.400||105.778||0.311||143||7.248||0.015||1.036||0.009||0.383||54.130||59.954||0.246||217||4.990||0.025||1.177||0.030||0.836||54.999||28.447||0.271||353||4.818||0.024||1.147||0.028||0.655||54.745||26.714||0.250||545||4.682||0.044||1.161||0.036||0.544||54.876||26.535||0.339||857||4.325||0.055||1.393||0.076||0.876||54.779||24.244||0.193||
||border=1 width=1000 align=center||!Statistics of the FEBeCoP Effective Beams for 100-353GHz Computed with the GH Mars12!||frequency||mean(fwhm)[[<<]][arcmin]||sd(fwhm)[[<<]][arcmin]||mean(e)||sd(e)||mean(psi)[[<<]][degree]||sd(psi)[[<<]][degree]||mean(Solid Angle)[[<<]][arcmin'^2^']||sd(Solid Angle)[[<<]][arcmin'^2^']||100||9.568||0.014||1.182||0.015||0.084||55.330||102.839||0.297||143||7.228||0.015||1.036||0.009||0.387||54.093||59.360||0.248||217||4.989||0.026||1.177||0.030||0.861||54.942||28.337||0.272||353||4.819||0.024||1.149||0.028||0.843||54.825||26.576||0.250||
||! #deliv %maroon%FEBeCoP deliverables
||border=1 width=700 align=center||!Band averaged beam solid angles!||Band||Omega_beam[[<<]][arcmin'^2^']||Monte Carlo error[[<<]][arcmin'^2^']||spatial variation[[<<]][arcmin'^2^']||bias[[<<]][arcmin'^2^']||FWHM_eff (Gaussian fit)[[<<]][arcmin]||100||105.78||---||0.31||---||9.66 (9.65)||143||59.95||---||0.25||---||7.27 (7.25)||217||28.45||---||0.27||---||5.01 (4.99)||353||26.71||---||0.25||---||4.86 (4.82)||545||26.54||---||0.34||---||4.84 (4.68)||857||24.24||---||0.19||---||4.63 (4.33)||
||%maroon% Beam solid angles for the PCCS
||border=1 width=700 align=center||!Band averaged beam solid angles!||Band||Omega_beam[[<<]][arcmin'^2^']||spatial variation[[<<]][arcmin'^2^']||Omega_beam_1[[<<]][arcmin'^2^']||spatial variation-1[[<<]][arcmin'^2^']||Omega_beam_2[[<<]][arcmin'^2^']||spatial variation-2[[<<]][arcmin'^2^']||100||105.778||0.311||100.830||0.410||105.777||0.311||143||59.954||0.246||56.811||0.419||59.952||0.246||217||28.447||0.271||26.442||0.537||28.426||0.271||353||26.714||0.250||24.827||0.435||26.653||0.250||545||26.535||0.339||24.287||0.455||26.302||0.337||857||24.244||0.193||22.646||0.263||23.985||0.191||
FEBeCoP, or Fast Effective Beam Convolution in Pixel space, is an approach to representing and computing effective beams (including both intrinsic beam shapes and the effects of scanning) that comprises the following steps:
In order to fix the convention of presentation of the scanning and effective beams, we show the classic view of the Planck focal plane as seen by the incoming CMB photon. The scan direction is marked, and the toward the center of the focal plane is at the 85 deg angle w.r.t spin axis pointing upward in the picture.
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.
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.
Effective beams are located at nersc: ??
and in both the HFI and LFI DPCs at:
Interface modules were developed to easily access the beams and the PSFs from the disk and the database. For HFI: The codes for reading the beams/PSFs and demonstration programs (http://cvs.planck.fr/cvs/Level2/Task_pkg/HL2_FEBeCoP/) FOr LFI:
There are two sets of (serial) demonstration programs:
A detailed README on the usage of the routines and the programs are available as: http://cvs.planck.fr/cvs/Level2/Task_pkg/HL2_FEBeCoP/README.txt included here:
How to use FEBeCoP effective beams and PSFs on magiqueIII
Is this of any relevance? external users don't use M3
The methodology for computing effective beams for a scanning CMB experiment like Planck was presented in our paper: http://arxiv.org/pdf/1005.1929
For easy access to the FEBeCoP beams and PSFs computed on NERSC, they have been transferred to magiqueIII. They are currently stored at two locations:
1. Hard disk: /space/SimuData/effBeam_HFI_v41 2. DMC group: /data/dmc/MISS01/DATA/FEBeCoP_v41
The gory details of how binary data is organized in the files / DMC objects are not essential to the user and may also change in the future. Here we present how the FEBeCoP I/O interface (installed and tested on magiqueIII) can be used to read effective beams and PSFs for any given set of pixels.
At present, the Fortran routines are available as .f90 sources, they will be available as a compiled library in future. getBeam.f90 can be used read beams from the disk and getBeam_PIO.f90 to read from the database.
Example Fortran programs and Makefiles to load beams/PSFs either from disk or from database and make their .fits skymaps are in:
List of programs
beam_extract_f : extract beams from disk beam_extract_f_PIO : extract beams from database psf_extract_f : extract PSF from disk psf_extract_f_PIO : extract PSF from database effConv : convolve map reading beam from disk effConv_PIO : convolve map reading beam from database
Example parameter files with brief explanations are provided in: http://cvs.planck.fr/cvs/Level2/Task_pkg/HL2_FEBeCoP/params/
Details on the subroutines
(Please look at the appropriate routines to get the exact syntax)
The basic scheme to load the beams/PSFs (in Fortran or IDL) has two steps:
"beaminfo" (output of this routine, users need not worry about this)
"prefix" is the prefix to the beam files or DMC objects, e.g., for 100GHz beams
from disk: prefix=/data/smitra/effBeam_HFI_v41/100/beams_
from DMC: prefix=/data/dmc/MISS01/DATA/FEBeCoP_v41/100_
"beam"/"psf" structure describes beams/PSFs using the following elements:
pix : (int_32) pixel index of the beam centre
nlist : (int_32) number of pixels used to describe the beam (typically ~200)
listpix : (nlist int_32) list of pixel indices describing the beam
map : (nlist or 6 x nlist float_32) values at the pixels listed in listpix
nobs : (1 or 6 float_64) effective number of observation matrix
"pixlist" is the list of pixels for which beam should be loaded
"npixel" number of pixels for which beam should be loaded
A detailed description of the data format of each file, including header keywords for fits files, extension names, column names, formats….
Cosmic Microwave background
(Hierarchical Equal Area isoLatitude Pixelation of a sphere, <ref name="Template:Gorski2005">HEALPix: A Framework for High-Resolution Discretization and Fast Analysis of Data Distributed on the Sphere, K. M. Górski, E. Hivon, A. J. Banday, B. D. Wandelt, F. K. Hansen, M. Reinecke, M. Bartelmann, ApJ, 622, 759-771, (2005).
(Planck) High Frequency Instrument
Early Release Compact Source Catalog
Flexible Image Transfer Specification
Data Processing Center
(Planck) Low Frequency Instrument
Data Management Component, the databases used at the HFI and LFI DPCs