Issue |
A&A
Volume 522, November 2010
|
|
---|---|---|
Article Number | A94 | |
Number of page(s) | 29 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361/200912606 | |
Published online | 05 November 2010 |
Residual noise covariance for Planck low-resolution data analysis
1
University of Helsinki, Department of Physics,
PO Box 64, 00014
Helsinki,
Finland
e-mail: reijo.t.keskitalo@jpl.nasa.gov; reijo.keskitalo@gmail.com
2
Helsinki Institute of Physics, PO Box 64, 00014
Helsinki,
Finland
3
Jet Propulsion Laboratory, California Institute of Technology,
4800 Oak Grove
Drive, Pasadena
CA
91109,
USA
4
Astrophysics Group, Cavendish Laboratory,
J J Thomson Avenue,
Cambridge
CB3 0HE,
UK
5
Institute of Astronomy, Madingley Road, Cambridge
CB3 0HA,
UK
6
Dipartimento di Fisica, Universitá di Roma “La
Sapienza”, p.le A. Moro
2, 00185
Roma,
Italy
7
Dipartimento di Fisica, Universitá di Roma “Tor
Vergata”, via della Ricerca
Scientifica 1, 00133
Roma,
Italy
8
Computational Cosmology Center, Lawrence Berkeley National
Laboratory, Berkeley
CA
94720,
USA
9
Metsähovi Radio Observatory, Helsinki University of Technology,
Metsähovintie 114,
02540
Kylmälä,
Finland
10
Laboratoire Astroparticule & Cosmologie (APC) – UMR
7164, CNRS, Université Paris Diderot, 10 rue A. Domon et L. Duquet, 75205
Paris Cedex 13,
France
11
Space Sciences Laboratory, University of California Berkeley,
Berkeley
CA
94720,
USA
12
INAF-IASF Bologna, Istituto di Astrofisica Spaziale e Fisica
Cosmica di Bologna Istituto Nazionale di Astrofisica, via Gobetti 101,
40129
Bologna,
Italy
13
Institute of Theoretical Astrophysics, University of Oslo,
PO Box 1029
Blindern, 0315
Oslo,
Norway
14
Centre of Mathematics for Applications, University of Oslo,
PO Box 1053
Blindern, 0316
Oslo,
Norway
15
INFN, Sezione di Bologna, Via Irnerio 46,
40126
Bologna,
Italy
16
INAF-OAB, Osservatorio Astronomico di Bologna Istituto Nazionale
di Astrofisica, via Ranzani 1, 40127
Bologna,
Italy
17
Warsaw University Observatory, Aleje Ujazdowskie 4, 00478
Warszawa,
Poland
18
Institut d’Astrophysique de Paris, 98bis boulevard Arago, 75014
Paris,
France
19
Department of Physics, Blackett Laboratory,
Imperial College London, South Kensington
campus, London,
SW7 2AZ,
UK
20
INFN, Sezione di “Tor Vergata”, via della Ricerca Scientifica 1,
00133
Roma,
Italy
21
Instituto de Fisica de Cantabria, CSIC-Universidad de Cantabria,
Avda. Los Castros
s/n, 39005
Santander,
Spain
22
ASI Science Data Center, c/o ESRIN, via G. Galilei snc,
00044
Frascati,
Italy
23
INAF-Osservatorio Astronomico di Roma, via di Frascati 33,
00040
Monte Porzio Catone,
Italy
Received:
31
May
2009
Accepted:
15
June
2010
Aims. We develop and validate tools for estimating residual noise covariance in Planck frequency maps, we also quantify signal error effects and compare different techniques to produce low-resolution maps.
Methods. We derived analytical estimates of covariance of the residual noise contained in low-resolution maps produced using a number of mapmaking approaches. We tested these analytical predictions using both Monte Carlo simulations and by applying them to angular power spectrum estimation. We used simulations to quantify the level of signal errors incurred in the different resolution downgrading schemes considered in this work.
Results. We find excellent agreement between the optimal residual noise covariance matrices and Monte Carlo noise maps. For destriping mapmakers, the extent of agreement is dictated by the knee frequency of the correlated noise component and the chosen baseline offset length. Signal striping is shown to be insignificant when properly dealt with. In map resolution downgrading, we find that a carefully selected window function is required to reduce aliasing to the subpercent level at multipoles, ℓ > 2Nside, where Nside is the HEALPix resolution parameter. We show that, for a polarization measurement, reliable characterization of the residual noise is required to draw reliable constraints on large-scale anisotropy.
Conclusions. Methods presented and tested in this paper allow for production of low-resolution maps with both controlled sky signal error level and a reliable estimate of covariance of the residual noise. We have also presented a method for smoothing the residual noise covariance matrices to describe the noise correlations in smoothed, bandwidth-limited maps.
Key words: cosmic microwave background / cosmology: observations / methods: data analysis / methods: numerical
© ESO, 2010
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