Making maps from Planck LFI 30 GHz data with asymmetric beams and cooler noise

The Planck satellite will observe the full sky at nine frequencies from 30 to 857 GHz. Temperature and polarization frequency maps made from these observations are prime deliverables of the Planck mission. The goal of this paper is to examine the effects of four realistic instrument systematics in the 30 GHz frequency maps: non-axially-symmetric beams, sample integration, sorption cooler noise, and pointing errors. We simulated one-year long observations of four 30 GHz detectors. The simulated timestreams contained cosmic microwave background (CMB) signal, foreground components ( both galactic and extra-galactic), instrument noise ( correlated and white), and the four instrument systematic effects. We made maps from the timelines and examined the magnitudes of the systematics effects in the maps and their angular power spectra. We also compared the maps of different mapmaking codes to see how they performed. We used five mapmaking codes ( two destripers and three optimal codes). None of our mapmaking codes makes any attempt to deconvolve the beam from its output map. Therefore all our maps had similar smoothing due to beams and sample integration. This is a complicated smoothing, because each map pixel has its own effective beam. Temperature to polarization cross-coupling due to beam mismatch causes a detectable bias in the TE spectrum of the CMB map. The effects of cooler noise and pointing errors did not appear to be major concerns for the 30 GHz channel. The only essential difference found so far between mapmaking codes that affects accuracy ( in terms of residual root-mean-square) is baseline length. All optimal codes give essentially indistinguishable results. A destriper gives the same result as the optimal codes when the baseline is set short enough ( Madam). For longer baselines destripers (Springtide and Madam) require less computing resources but deliver a noisier map.The Planck satellite will observe the full sky at nine frequencies from 30 to 857 GHz. Temperature and polarization frequency maps made from these observations are prime deliverables of the Planck mission. The goal of this paper is to examine the effects of four realistic instrument systematics in the 30 GHz frequency maps: non-axially-symmetric beams, sample integration, sorption cooler noise, and pointing errors. We simulated one-year long observations of four 30 GHz detectors. The simulated timestreams contained cosmic microwave background (CMB) signal, foreground components ( both galactic and extra-galactic), instrument noise ( correlated and white), and the four instrument systematic effects. We made maps from the timelines and examined the magnitudes of the systematics effects in the maps and their angular power spectra. We also compared the maps of different mapmaking codes to see how they performed. We used five mapmaking codes ( two destripers and three optimal codes). None of our mapmaking codes makes any attempt to deconvolve the beam from its output map. Therefore all our maps had similar smoothing due to beams and sample integration. This is a complicated smoothing, because each map pixel has its own effective beam. Temperature to polarization cross-coupling due to beam mismatch causes a detectable bias in the TE spectrum of the CMB map. The effects of cooler noise and pointing errors did not appear to be major concerns for the 30 GHz channel. The only essential difference found so far between mapmaking codes that affects accuracy ( in terms of residual root-mean-square) is baseline length. All optimal codes give essentially indistinguishable results. A destriper gives the same result as the optimal codes when the baseline is set short enough ( Madam). For longer baselines destripers (Springtide and Madam) require less computing resources but deliver a noisier map.The Planck satellite will observe the full sky at nine frequencies from 30 to 857 GHz. Temperature and polarization frequency maps made from these observations are prime deliverables of the Planck mission. The goal of this paper is to examine the effects of four realistic instrument systematics in the 30 GHz frequency maps: non-axially-symmetric beams, sample integration, sorption cooler noise, and pointing errors. We simulated one-year long observations of four 30 GHz detectors. The simulated timestreams contained cosmic microwave background (CMB) signal, foreground components ( both galactic and extra-galactic), instrument noise ( correlated and white), and the four instrument systematic effects. We made maps from the timelines and examined the magnitudes of the systematics effects in the maps and their angular power spectra. We also compared the maps of different mapmaking codes to see how they performed. We used five mapmaking codes ( two destripers and three optimal codes). None of our mapmaking codes makes any attempt to deconvolve the beam from its output map. Therefore all our maps had similar smoothing due to beams and sample integration. This is a complicated smoothing, because each map pixel has its own effective beam. Temperature to polarization cross-coupling due to beam mismatch causes a detectable bias in the TE spectrum of the CMB map. The effects of cooler noise and pointing errors did not appear to be major concerns for the 30 GHz channel. The only essential difference found so far between mapmaking codes that affects accuracy ( in terms of residual root-mean-square) is baseline length. All optimal codes give essentially indistinguishable results. A destriper gives the same result as the optimal codes when the baseline is set short enough ( Madam). For longer baselines destripers (Springtide and Madam) require less computing resources but deliver a noisier map.Peer reviewe

Constraints on the Strength of a Primordial Magnetic Field from Big Bang Nucleosynthesis

The effects of magnetic fields on Big Bang Nucleosynthesis(BBN) have been calculated, and the impact on the abundances of the light elements have been investigated numerically. An upper limit on the strength of primordial magnetic fields compatible with observations of light element abundances has been thus obtained. In the framework of standard BBN theory, the maximum strength of the primordial magnetic fields, on scales greater than $10^4$cm but smaller than the event horizon at the BBN epoch ($\sim 1$ min., $\sim 2\times 10^{12}$cm), is $\le 10^{11}$ Gauss. This limit is shown to allow magnetic fields at the time of recombination no stronger than $\sim 0.1$ gauss on scales $\ge 10^{11}{\rm cm}$. Our results also strongly indicate that, at the BBN epoch, and for field strengths $B\le10^{13}$gauss, the effects of magnetic fields on the primordial abundances of light elements are dominated by effects from reaction rates in the presense of primeval magnetic fields rather than by magnetic density effects on the expansion rate.Comment: 17 pages in Plain TeX plus 5 tables and 7 figures; FNAL preprin