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Published August 2007 | Published
Journal Article Open

Making maps from Planck LFI 30GHz data

Abstract

This paper is one of a series describing the performance and accuracy of map-making codes as assessed by the Planck CTP working group. We compare the performance of multiple codes written by different groups for making polarized maps from Planck-sized, all-sky cosmic microwave background (CMB) data. Three of the codes are based on a destriping algorithm, whereas the other three are implementations of a maximum-likelihood algorithm. Previous papers in the series described simulations at 100 GHz (Poutanen et al. 2006, A&A, 449, 1311) and 217 GHz (Ashdown et al. 2007, A&A, 467, 761). In this paper we make maps (temperature and polarisation) from the simulated one-year observations of four 30 GHz detectors of Planck Low Frequency Instrument (LFI). We used Planck Level S simulation pipeline to produce the observed time-ordered-data streams (TOD). Our previous studies considered polarisation observations for the CMB only. For this paper we increased the realism of the simulations and included polarized galactic foregrounds in our sky model, which is based on the version 0.1 of the PLANCK reference sky. Our simulated TODs comprised dipole, CMB, diffuse galactic emissions, extragalactic radio sources, and detector noise. The strong subpixel signal gradients arising from the foreground signals couple to the output map through the map-making and cause an error (signal error) in the maps. Destriping codes have smaller signal error than the maximum-likelihood codes. We examined a number of schemes to reduce this error. On the other hand, the maximum-likelihood map-making codes can produce maps with lower residual noise than destriping codes.

Additional Information

The work reported in this paper was done by the CTP Working Group of the Planck Consortia. Planck is a mission of the European Space Agency. The authors would like to thank Institut d'Astrophysique de Paris (IAP) for its hospitality in June 2005 when the CTP Working Group met to undertake this work. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under Contract No. DE-AC03-76SF00098. We acknowledge the use of version 0.1 of the Planck reference sky model, prepared by the members of the Planck Working Group 2 and available at http://www.planck.fr/heading79.html. This work has made use of the Planck satellite simulation package (Level S), which is assembled by the Max Planck Institute for Astrophysics Planck Analysis Centre (MPAC). CB was supported in part by the NASA LTSA grant NNG04GC90G. EK and TP were supported by the Academy of Finland grants no. 205800, 213984, and 214598. They also thank the von Frenckell foundation for financial support. RS acknowledges support of the Marie Curie IRG (FY2006) grant. Some of the results in this paper have been derived using the HEALPix package (Górski et al. 1999, 2005a). The US Planck Project is supported by the NASA Science Mission Directorate.

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August 22, 2023
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