Difference between revisions of "Astrophysical component maps test"
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Revision as of 18:30, 1 March 2013
Contents
Maps of astrophysical foregrounds[edit]
We describe diffuse foreground products for the Planck 2013 release. See Planck paper P06-Component Separation #planck2013-p06 for a detailed description and astrophysical discussion of those.
Product description[edit]
Low frequency foreground component[edit]
The products below contain the result of the fitting for one foreground component at low frequencies in Planck bands, along with its spectral behavior parametrized by a power law spectral index. Amplitude and spectral indeces are evaluated at Nside 256 (see below in the production process), along with standard deviation from sampling and instrumental noise on both. An amplitude solution at Nside=2048 is also given, along with standard deviation from sampling and instrumental noise as well as solutions on halfrings. The beam profile associated to this component is also provided as a secondary Extension in the Nside 2048 product.
Thermal dust[edit]
The products below contain the result of the fitting for one foreground component at high frequencies in Planck bands, along with its spectral behavior parametrized by temperature and emissivity. Amplitude, temperature and emissivity are evaluated at Nside 256 (see below in the production process), along with standard deviation from sampling and instrumental noise on all of them. An amplitude solution at Nside=2048 is also given, along with standard deviation from sampling and instrumental noise as well as solutions on halfrings. The beam profile associated to this component is provided.
Sky mask[edit]
The delivered mask is defined as the sky region where the fitting procedure was conducted and the solutions presented here were obtained. It is made by masking a region where the Galactic emission is too intense to perform the fitting, plus the masking of brightest point sources.
Production process[edit]
CODE: COMMANDER-RULER. The code exploits a parametrization of CMB and main diffuse foreground observables. The naive resolution of input frequency channels is reduced to Nside=256 first. Parameters related to the foreground scaling with frequency are estimated at that resolution by using Markov Chain Monte Carlo analysis using Gibbs sampling. The foreground parameters make the foreground mixing matrix which is applied to the data at full resolution in order to obtain the provided products at Nside=2048. In the Planck paper P06-Component Separation #planck2013-p06 additional material is discussed, specifically concerning the sky region where the solutions are reliable, in terms of chi2 maps.
Inputs[edit]
Nominal frequency maps at 30, 44, 70, 100, 143, 217, 353 GHz (LFI 30 GHz frequency maps, LFI 44 GHz frequency maps and LFI 70 GHz frequency maps, HFI 100 GHz frequency maps, HFI 143 GHz frequency maps,HFI 217 GHz frequency maps and HFI 353 GHz frequency maps) and their II column corresponding to the noise covariance matrix. Halfrings at the same frequencies. Beam window functions as reported in the LFI and HFI RIMO.
Related products[edit]
None.
File names[edit]
Low frequency component at Nside 256: COM_CompMap_Lfreqfor-commrul_0256_R1.00.fits
Low frequency component at Nside 2048: COM_CompMap_Lfreqfor-commrul_2048_R1.00.fits
Thermal dust at Nside 256: COM_CompMap_dust-commrul_0256_R1.00.fits
Thermal dust at Nside 2048: COM_CompMap_dust-commrul_2048_R1.00.fits
Mask: COM_CompMap_Mask-rulerminimal_2048.fits
Meta Data[edit]
Low frequency foreground component[edit]
Low frequency component at Nside 256[edit]
File name: COM_CompMap_Lfreqfor-commrul_0256_R1.00.fits
Name HDU -- COMP-MAP
Column 1: I -- uK_CMB
Column 2: I_stdev -- uK_CMB
Column 3: Beta -- No Unit
Column 4: B_stdev -- No Unit
Comment: The Intensity is normalized at 30 GHz
Comment: The intensity was estimated during mixing matrix estimation
Low frequency component at Nside 2048[edit]
File name: COM_CompMap_Lfreqfor-commrul_2048_R1.00.fits
Name HDU -- COMP-MAP
Column 1: I -- uK_CMB
Column 2: I_stdev -- uK_CMB
Column 3: I_hr1 -- uK_CMB
Column 4: I_hr2 -- uK_CMB
Comment: The intensity was computed after mixing matrix application
Nome HDU -- BeamWF
Column 1: Temperature (meaning the beam profile) -- None
Comment: Beam window function used in the Component separation process
Thermal dust[edit]
Thermal dust component at Nside=256[edit]
File name: COM_CompMap_dust-commrul_0256_R1.00.fits
Name HDU -- COMP-MAP
Column 1: I -- MJy/sr
Column 2: I_stdev -- MJy/sr
Column 3: Em -- none
Column 4: Em_stdev -- none
Column 5: T -- uK_CMB
Column 6: T_stdev -- uK_CMB
COMMENT: The intensity is normalized at 353 GHz
Thermal dust component at Nside=2048[edit]
File name: COM_CompMap_dust-commrul_2048_R1.00.fits
Name HDU -- COMP-MAP
Column 1: I -- MJy/sr
Column 2: I_stdev -- MJy/sr
Column 2: I_hr1 -- MJy/sr
Column 3: I_hr2 -- MJy/sr
Name HDU -- BeamWF
Column 1: Temperature (meaning the beam profile) -- None
Comment: Beam window function used in the Component separation process
Sky mask[edit]
File name: COM_CompMap_Mask-rulerminimal_2048.fits
Nome HDU -- COMP-MASK
Column 1: Mask
Dust optical depth map and model[edit]
Thermal emission from interstellar dust is captured by Planck-HFI over the whole sky, at all frequencies from 100 to 857 GHz. This emission is well modelled by a modified black body in the far-infrared to millimeter range. It is produced by the biggest interstellar dust grain that are in thermal equilibrium with the radiation field from stars. The grains emission properties in the sub-millimeter are therefore directly linked to their absorption properties in the UV-visible range. By modelling the thermal dust emission in the sub-millimeter, a map of dust reddening in the visible can then be constructed.
Model of thermal dust emission
The model of the thermal dust emission is based on a modify black body fit to the data I_nu:
I_nu = A B_nu(T) nu^beta.
where B_nu(T) is the Planck function for dust equilibirum temperature T, A is the amplitude of the MBB and beta the dust spectral index. The dust optical depth at frequency nu is :
Tau_nu = I_nu / B_nu(T) = A nu^beta
The dust parameters provided are T, beta and Tau_353. They were obtained by fitting the Planck data at 353, 545 and 857 GHz together with the IRAS (IRIS) 100 micron data. All maps (in Healpix nside=2048) were smoothed to a common resolution of 5 arcmin. The CMB anisotropies, clearly visible at 353 GHz, were removed from all the HFI maps using the SMICA map. An offset was removed from each map to obtained a meaningful Galactic zero level, using a correlation with the LAB 21 cm data in diffuse areas of the sky (N_HI < 2x10^20 cm^-2). Because the dust emission is so well correlated between frequencies in the Rayleigh-Jeans part of the dust spectrum, the zero level of the 545 and 353 GHz were improved by correlating with the 857 GHz over a larger mask (N_HI < 3x10^20 cm^-2). Faint residual dipole structures, identified in the 353 and 545 GHz maps, were removed prior to the fit.
The MBB fit was performed using a chi-square minimization, assuming errors for each data point that include instrumental noise, calibration uncertainties (on both the dust emission and the CMB anisotropies) and uncertainties on the zero level. Because of the known degeneracy between T and Beta in the presence of noise, we produced a model of dust emission using data smoothed to 35 arcmin; at such resolution no systematic bias of the parameters is observed. The map of the spectral index Beta at 35 arcmin was than used to fit the data for T and Tau_353 at 5 arcmin.
E(B-V) map :
For the production of the E(B-V) map, we used Planck and IRAS data from which point sources in diffuse areas were removed to avoid contamination by galaxies.
In the hypothesis of constant dust emission cross-section, the optical depth map Tau_353 is proportional to dust column density. It can then be used to estimate E(B-V), also proportional to dust column density in the hypothesis of a constant differential absorption cross-section between the B and V bands. Given those assumptions :
E(B-V) = q Tau_353.
To estimate the calibration factor q, we followed a method similar to Mortsell (2013) based on SDSS reddening measurements (E(g-r) which corresponds closely to E(B-V)) of 77 429 Quasars (Schneider et al. 2007). The interstellar HI column densities covered on the lines of sight of this sample ranges from 0.5 to 10x10^20 cm^-2. Therefore this sample allows to estimate q in the diffuse ISM where dust properties are expected to vary less than in denser clouds where coagulation and grain growth might modify dust emission and absorption cross sections.
Dust optical depth products
The characteristics of the dust model maps are the following.
- Dust temperature : nside 2048, fwhm=5 arcmin, units=Kelvin
- Dust spectral index : nside=2048, fwhm=35 arcmin, no units
- Dust optical depth at 353 GHz : nside=2048, fwhm=5 arcmin, no units
- Dust reddening E(B-V) : nside=2048, fwhm=5 arcmin, units=magnitude, obtained with data from which point sources were removed.
These maps and their associated uncertainty maps are written into a single extension whose structure is shows below.
;----------------------------------------------------------------------------- ; EXTENSION 1: COMP-MAP ; - Header ;----------------------------------------------------------------------------- MRDFITS: Binary table. 8 columns by 1 rows. XTENSION= 'BINTABLE' /Written by IDL: Mon Feb 4 11:33:34 2013 BITPIX = 8 / NAXIS = 2 /Binary table NAXIS1 = 1610612736 /Number of bytes per row NAXIS2 = 1 /Number of rows PCOUNT = 0 /Random parameter count GCOUNT = 1 /Group count TFIELDS = 8 /Number of columns COMMENT COMMENT *** End of mandatory fields *** COMMENT EXTVER = 1 /Extension version DATE = '2013-02-04' /Creation date COMMENT COMMENT *** Column names *** COMMENT TTYPE1 = 'TAU353 ' / opacity 353GHz TTYPE2 = 'TAU353ERR' / opacity 353GHz TTYPE3 = 'A_V ' / Extinction TTYPE4 = 'A_V_ERR ' / Error on A_V TTYPE5 = 'T_HF ' / T for hi freq correction TTYPE6 = 'T_HF_ERR' / T for hi freq correction TTYPE7 = 'BETAHF ' / Beta for hi freq correction TTYPE8 = 'BETAHFERR' / Mask COMMENT COMMENT *** Column formats *** COMMENT TFORM1 = '50331648E' / TFORM2 = '50331648E' / TFORM3 = '50331648E' / TFORM4 = '50331648E' / TFORM5 = '50331648E' / TFORM6 = '50331648E' / TFORM7 = '50331648E' / TFORM8 = '50331648E' / COMMENT COMMENT *** Column units *** COMMENT TUNIT1 = 'none ' / TUNIT2 = 'none ' / TUNIT3 = 'mag ' / TUNIT4 = 'mag ' / TUNIT5 = 'K ' / TUNIT6 = 'K ' / TUNIT7 = 'none ' / TUNIT8 = 'none ' / COMMENT COMMENT *** Planck params *** COMMENT EXTNAME = 'COMP-MAP' / Extension name AST-COMP= 'DUST_OPA' / Component COORSYS = 'GALACTIC' / Coordinate system ORDERING= 'NESTED ' / Healpix ordering NSIDE = 2048 / Healpix Nside FIRSTPIX= 0 / LASTPIX = 50331647 / BAD_DATA= -1.63750E+30 / bad pixel value FILENAME= 'HFI_CompMap_DustOpacity_2048_R1.00.fits' / FITS filename CHECKSUM= '7DPW8CMU7CMU7CMU' / HDU checksum created 2013-02-04T10:33:35 PROCVER = 'DX9 ' / Product version COMMENT COMMENT see Planck Eplanatory Supplement Ch. 999 for COMMENT for description of the model and how to use it. COMMENT END
CO emission maps[edit]
CO rotational transition line emission is present in all HFI bands but for the 143 GHz channel. It is especially significant in the 100, 217 and 353 GHz channels (due to the 115 (1-0), 230 (2-1) and 345 GHz (3-2) CO transitions). This emission comes essentially from the Galactic interstellar medium and is mainly located at low and intermediate Galactic latitudes. Three approaches (summarised below) have been used to extract CO velocity-integrated emission maps from HFI maps and to make three types of CO products. An introduction is given in Section and a full description of these products is given in #planck2013-p03a.
- Type 1 product: it is based on a single channel approach using the fact that each CO line has a slightly different transmission in each bolometer at a given frequency channel. These transmissions can be evaluated from bandpass measurements that were performed on the ground or empirically determined from the sky using existing ground-based CO surveys. From these, the J=1-0, J=2-1 and J=3-2 CO lines can be extracted independently. As this approach is based on individual bolometer maps of a single channel, the resulting Signal-to-Noise ratio (SNR) is relatively low. The benefit, however, is that these maps do not suffer from contamination from other HFI channels (as is the case for the other approaches) and are more reliable, especially in the Galactic Plane.
- Type 2 product: this product is obtained using a multi frequency approach. Three frequency channel maps are combined to extract the J=1-0 (using the 100, 143 and 353 GHz channels) and J=2-1 (using the 143, 217 and 353 GHz channels) CO maps. Because frequency channels are combined, the spectral behaviour of other foregrounds influences the result. The two type 2 CO maps produced in this way have a higher SNR than the type 1 maps at the cost of a larger possible residual contamination from other diffuse foregrounds.
- Type 3 product: using prior information on CO line ratios and a multi-frequency component separation method, we construct a combined CO emission map with the largest possible SNR. This type 3 product can be used as a sensitive finder chart for low-intensity diffuse CO emission over the whole sky.
The released Type 1 CO maps have been produced using the MILCA-b algorithm, Type 2 maps using a specific implementation of the Commander algorithm, and the Type 3 map using the full Commander-Ruler component separation pipeline (see above).
Characteristics of the released maps are the following. We provide Healpix maps with Nside=2048. For one transition, the CO velocity-integrated line signal map is given in K_RJ.km/s units. A conversion factor from this unit to the native unit of HFI maps (K_CMB) is provided in the header of the data files and in the RIMO. Four maps are given per transition and per type:
- The signal map
- The standard deviation map (same unit as the signal),
- A null test noise map (same unit as the signal) with similar statistical properties. It is made out of half the difference of half-ring maps.
- A mask map (0B or 1B) giving the regions (1B) where the CO measurement is not reliable because of some severe identified foreground contamination.
All products of a given type belong to a single file. Type 1 products have the native HFI resolution i.e. approximately 10, 5 and 5 arcminutes for the CO 1-0, 2-1, 3-2 transitions respectively. Type 2 products have a 15 arcminute resolution The Type 3 product has a 5.5 arcminute resolution.
A typical header for these data is given below. It contains a keyword giving the conversion between the CO velocity-integrated units (K.km/s) and the HFI map native units (K_CMB). However, users are to use CO subtraction with care, as it will necessarily add noise to the result.
XTENSION= 'BINTABLE' /Written by IDL: Fri Dec 14 14:29:27 2012 BITPIX = 8 / NAXIS = 2 /Binary table NAXIS1 = 1308622848 /Number of bytes per row NAXIS2 = 1 /Number of rows PCOUNT = 0 /Random parameter count GCOUNT = 1 /Group count TFIELDS = 8 /Number of columns COMMENT COMMENT *** End of mandatory fields *** COMMENT EXTVER = 1 /Extension version DATE = '2012-12-14' /Creation date COMMENT COMMENT *** Column names *** COMMENT TTYPE1 = 'I10 ' / Intensity TTYPE2 = 'E10 ' / Error TTYPE3 = 'N10 ' / Nulltest TTYPE4 = 'M10 ' / Mask TTYPE5 = 'I21 ' / Intensity TTYPE6 = 'E21 ' / Error TTYPE7 = 'N21 ' / Nulltest TTYPE8 = 'M21 ' / Mask COMMENT COMMENT *** Column formats *** COMMENT TFORM1 = '50331648E' / TFORM2 = '50331648E' / TFORM3 = '50331648E' / TFORM4 = '50331648B' / TFORM5 = '50331648E' / TFORM6 = '50331648E' / TFORM7 = '50331648E' / TFORM8 = '50331648B' / COMMENT COMMENT *** Column units *** COMMENT TUNIT1 = 'Krj km/s' / TUNIT2 = 'Krj km/s' / TUNIT3 = 'Krj km/s' / TUNIT4 = 'none ' / TUNIT5 = 'Krj km/s' / TUNIT6 = 'Krj km/s' / TUNIT7 = 'Krj km/s' / TUNIT8 = 'none ' / COMMENT COMMENT *** Planck params *** COMMENT EXTNAME = 'COMP-MAP' / Extension name AST-COMP= 'CO-LINE ' / Component COORSYS = 'GALACTIC' / Coordinate system ORDERING= 'NESTED ' / Healpix ordering NSIDE = 2048 / Healpix Nside FIRSTPIX= 0 / LASTPIX = 50331647 / BAD_DATA= -1.63750E+30 / bad pixel value FILENAME= 'HFI_CompMap_CO-line_2048_R1.01.fits' / FITS filename PROCVER = 'DX9 ' / Product version COMMENT COMMENT Multiply by these factors to convert Kcmb COMMENT CNV(1-0)= 1.42144524614E-05 / Conv factor in Kcmb/(Krj*km/s) CNV(2-1)= 4.43577255985E-05 / Conv factor in Kcmb/(Krj*km/s) COMMENT COMMENT ------------------------------------------------------------------------ COMMENT HFI-DMC objects: COMMENT group: /data/dmc/MISS03/DATA/CO_PRODUCT_TYPE2/ COMMENT Creation date - object name COMMENT 12-11-30 14:21 - 115GHz_CO_J1-0_type2 COMMENT 12-11-30 14:23 - 230GHz_CO_J2-1_type2 COMMENT 12-11-30 14:22 - 115GHz_CO_J1-0_STDDEV_type2 COMMENT 12-11-30 14:24 - 230GHz_CO_J2-1_STDDEV_type2 COMMENT 12-11-30 14:22 - 115GHz_CO_J1-0_NULL_type2 COMMENT 12-11-30 14:23 - 230GHz_CO_J2-1_NULL_type2 COMMENT 12-11-30 16:29 - 115GHz_CO_J1-0_MASK_type2 COMMENT 12-11-30 16:31 - 230GHz_CO_J2-1_MASK_type2 COMMENT ------------------------------------------------------------------------ END
Other maps[edit]
This section will be for the various CIB maps, and others. The overall structure of the FITS files will be similar to the cases above, though the details will be tailored to the individual products.
Cosmic Microwave background
(Planck) High Frequency Instrument
Flexible Image Transfer Specification
reduced IMO
Data Management Component, the databases used at the HFI and LFI DPCs
