Correction maps
Contents
General description[edit]
Different corrections have been applied to the 2018 data releases, and when available, correction maps are provided in PLA.
Below short description these corrections can be found, furthers details for LFI are avialable in Planck-2020-A2[1].
LFI Template[edit]
In the 2018 release an iterative schema for the phometric calibration has been adopted. In case of 70GHz this iterative procedure didn't converge at the time of the release. As a consequence, we expect that low-level residuals are still present in the 2018 LFI maps, with a pattern similar to that of the 2015 maps, though with significantly lower amplitude. For the 2018 release, we adopt the dfference between the two last iterations as a spatial template of residual gain uncertainties projected onto the sky. This template is used only at 70 GHz (already applyed in the maps released) and made available trought the PLA (see section 3 of Planck-2020-A2[1]).
LFI BandPass Leackage correction[edit]
BandPass Leackage correction estimation is described is section 7 of Planck-2020-A2[1]. We release BandPass corrected maps, BandPass uncorrected maps and BandPass correction Maps.
List of LFI Correction maps[edit]
| Type | Filename | Comment |
|---|---|---|
| 70GHz Template | LFI_CorrMap_070-Gain-tpl_1024_R3.00_full.fits | ONLY for the 70GHz |
| BandPass Correction full period | LFI_CorrMap_???-BPassCorr_1024_R3.00_full.fits | n/a |
| BandPass Correction full period Ring-Half | LFI_CorrMap_???-BPassCorr_1024_R3.00_full-ringhalf-?.fits | n/a |
| BandPass Correction single year | LFI_CorrMap_???-BPassCorr_1024_R3.00_year-?.fits | n/a |
| BandPass Correction year combination | LFI_CorrMap_???-BPassCorr_1024_R3.00_year?-?.fits | n/a |
| BandPass Correction survey combination | LFI_CorrMap_???-BPassCorr_1024_R3.00_survey-1-3-5-6-7-8.fits | n/a |
List of LFI A-maps[edit]
The small amplitude of the CMB polarized signal requires a careful handling of systematic effects capable of biasing polarization results. The dominant one is the leakage of unpolarized emission into polarization; any difference in bandpass between the two arms of an LFI radiometer will result in leakage into polarization. In the case of the CMB, this is not a problem. Since calibration of each radiometer uses the CMB dipole that has the same frequency spectrum of the CMB itself, exact gain calibration perfectly cancels out in polarization. However, unpolarized foreground emissions with spectra different from the CMB will appear with different amplitudes in the two arms, producing a leak into polarizaion. In order to derive a correction for this bandpass mismatch, we exploit the IQUSS approach (Page et al 2007) as in the 2015 release.
The main ingredients in the bandpass mismatch recipe are the leakage maps "L", the spurious maps "S_k" (see below), the "a-factors" and the "A_Q[U]" maps. The A_Q[U] produced for the 2018 release are then provided and available in the archive. For further details please refers to Planck-2020-A2[1] and Planck-2015-A03[2].
A_Q[U] Maps has been produced per radiometer and following the same Time split.
Example:
- LFI_Amap_RR_Z_fs_R3.00_period.fits
- LFI_Amap_RR_[Q-U]_fs_R3.00_year-[1-4].fits
- LFI_Amap_RR_U_fs_R3.00_year-3-4.fits
Where
- RR= Radiometer [18-23]
- Z = Stokes [Q-U]
- period = year-# [1-4]
- period = year-combination = year-#-# [1-4]
- period = survey-1-3-5-6-7-8
- period = full
- period = full-ringhalf-# [1-2]
References[edit]
- ↑ 1.01.11.21.3 Planck 2018 results. II. Low Frequency Instrument data processing, Planck Collaboration, 2020, A&A, 641, A2.
- ↑ Planck 2015 results. II. LFI processing, Planck Collaboration, 2016, A&A, 594, A2.
Planck Legacy Archive
(Planck) Low Frequency Instrument
Flexible Image Transfer Specification
Cosmic Microwave background
