Beam deconvolution in noisy CMB maps

Burigana, C.; Sáez, D.

doi:10.1051/0004-6361:20031038

Cited by 16 publications

(17 citation statements)

References 22 publications

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“…Recently, deconvolution mapmaking algorithms have been developed that can produce maps in which the smoothing of the beam response has been deconvolved. These methods lead to maps that approximate the true sky (Burigana & Sáez 2003, Armitage & Wandelt 2004, Harrison et al 2008). These methods are sufficiently different from the ones considered here that different methods of comparison must be used, and we therefore do not include detailed description of them in this paper.…”

Section: Results Of Mapmakingmentioning

confidence: 99%

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

Ashdown

Baccigalupi

Bartlett

et al. 2008

A&A

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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 an 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 every 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.

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Section: Results Of Mapmakingmentioning

confidence: 99%

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

Ashdown

Baccigalupi

Bartlett

et al. 2008

A&A

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“…So once a suitable basis is chosen, the rest of the analysis can be applied without requiring any major change. It may also be possible to deconvolve only a patch of the sky using a similar method [54].…”

Section: Fig 8 (Color Online)mentioning

confidence: 99%

Gravitational wave radiometry: Mapping a stochastic gravitational wave background

et al. 2008

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The problem of the detection and mapping of a stochastic gravitational wave background (SGWB), either cosmological or astrophysical, bears a strong semblance to the analysis of the cosmic microwave background (CMB) anisotropy and polarization, which too is a stochastic field, statistically described in terms of its correlation properties. An astrophysical gravitational wave background (AGWB) will likely arise from an incoherent superposition of unmodelled and/or unresolved sources and cosmological gravitational wave backgrounds (CGWB) are also predicted in certain scenarios. The basic statistic we use is the cross correlation between the data from a pair of detectors. In order to ''point'' the pair of detectors at different locations one must suitably delay the signal by the amount it takes for the gravitational waves (GW) to travel to both detectors corresponding to a source direction. Then the raw (observed) sky map of the SGWB is the signal convolved with a beam response function that varies with location in the sky. We first present a thorough analytic understanding of the structure of the beam response function using an analytic approach employing the stationary phase approximation. The true sky map is obtained by numerically deconvolving the beam function in the integral (convolution) equation. We adopt the maximum likelihood framework to estimate the true sky map using the conjugate gradient method that has been successfully used in the broadly similar, well-studied CMB map-making problem.We numerically implement and demonstrate the method on signal generated by simulated (unpolarized) SGWB for the GW radiometer consisting of the LIGO pair of detectors at Hanford and Livingston. We include ''realistic'' additive Gaussian noise in each data stream based on the LIGO-I noise power spectral density. The extension of the method to multiple baselines and polarized GWB is outlined. In the near future the network of GW detectors, including the Advanced LIGO and Virgo detectors that will be sensitive to sources within a thousand times larger spatial volume, could provide promising data sets for GW radiometry.

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“…At each observed position of the Leiden survey a) we first assigned the Stokes parameters corresponding to the Synfast simulation pixel in which it would project; and b) the corresponding rms given in the original table; c) we then added to each Stokes parameter a random value extracted from a Gaussian distribution in order to mimic the effect of the instrumental white noise (see, e.g., Burigana & Sáez 2003). The adopted standard deviation of this Gaussian distribution has been chosen equal to the mean error quoted for the considered original data.…”

Section: Interpolation Algorithm Optimization and Accuracymentioning

confidence: 99%

A multifrequency angular power spectrum analysis of the Leiden polarization surveys

Porta

Burigana

2006

A&A

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The Galactic synchrotron emission is expected to be the most relevant source of astrophysical contamination in cosmic microwave background polarization measurements, at least at frequencies ν < ∼ 70 GHz and at angular scales θ > ∼ 30 . We present a multifrequency analysis of the Leiden surveys, linear polarization surveys covering the Northern Celestial Hemisphere at five frequencies between 408 MHz and 1411 MHz. By implementing specific interpolation methods to deal with these irregularly sampled data, we produced maps of the polarized diffuse Galactic radio emission with a pixel size 0.92 • . We derived the angular power spectrum (APS) (PI, E, and B modes) of the synchrotron dominated radio emission as function of the multipole, . We considered the whole covered region and some patches at different Galactic latitudes. By fitting the APS in terms of power laws (C ∼ κ · α ), we found spectral indices that steepen with increasing frequency: from α ∼ −(1−1.5) at 408 MHz to α ∼ −(2−3) at 1411 MHz for 10 < ∼ < ∼ 100 and from α ∼ −0.7 to α ∼ −1.5 for lower multipoles (the exact values depending on the considered sky region and polarization mode). The bulk of this flattening at lower frequencies can be interpreted in terms of Faraday depolarization effects. We then considered the APS at various fixed multipoles and its frequency dependence. Using the APSs of the Leiden surveys at 820 MHz and 1411 MHz, we determined possible ranges for the rotation measure, RM, in the simple case of an interstellar medium slab model. Also taking into account the polarization degree at 1.4 GHz, it is possible to break the degeneracy between the identified RM intervals. The most reasonable of them turned out to be RM ∼ 9−17 rad/m 2 although, given the uncertainty on the measured polarization degree, RM values in the interval ∼53−59 rad/m 2 cannot be excluded.

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Beam deconvolution in noisy CMB maps

Cited by 16 publications

References 22 publications

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

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

Gravitational wave radiometry: Mapping a stochastic gravitational wave background

A multifrequency angular power spectrum analysis of the Leiden polarization surveys

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