Making maps from Planck LFI 30 GHz data

¹ Astrophysics Group, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, UK
² Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
³ Institut für Theoretische Astrophysik, Universität Heidelberg, Albert-Überle-Str. 2, 69120, Heidelberg, Germany
⁴ SISSA/ISAS, via Beirut 4, 34014 Trieste, and INFN, Sezione di Trieste, via Valerio 2, 34127 Trieste, Italy
⁵ Dipartimento di Fisica, Università di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
⁶ Laboratoire Astroparticule & Cosmologie, 10 rue A.Domon et L.Duquet, 75205 Paris Cedex 13, France (UMR 7164 CNRS, Université Paris 7, CEA, Observatoire de Paris)
⁷ Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720, USA
⁸ Space Sciences Laboratory, University of California Berkeley, Berkeley CA 94720, USA
⁹ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA 91109, USA
¹⁰ California Institute of Technology, Pasadena CA 91125, USA
¹¹ Warsaw University Observatory, Aleje Ujazdowskie 4, 00478 Warszawa, Poland
¹² University of Helsinki, Department of Physical Sciences, PO Box 64, 00014 Helsinki, Finland e-mail: hannu.kurki-suonio@helsinki.fi
¹³ Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, 75014 Paris, France
¹⁴ Helsinki Institute of Physics, PO Box 64, 00014 Helsinki, Finland
¹⁵ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
¹⁶ Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana IL 61801, USA
¹⁷ Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana IL 61801, USA

Received: 16 February 2007
Accepted: 29 May 2007

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.