Using the COBE/DMR data as a test-bed for normality assessments

Aghanim, N.; Forni, O.; Bouchet, F. R.

doi:10.1051/0004-6361:20000187

Cited by 35 publications

(40 citation statements)

References 19 publications

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“…These include the angular distribution of galaxies on the sky (Coles & Plionis 1991 ;Gott et al 1992), the distribution of galaxies in slices of the universe Colley 1997 ;Park, Gott, & Choi 2001), and the CMB temperature anisotropy Ðeld (Coles 1988 ;2000 ;Barreiro et al 2000 ;Aghanim, Forni, & Bouchet 2001;Phillips & Kogut 2001). While it has been argued that the DMR data shows slight evidence for non-Gaussianity, this has been attributed to non-CMB anisotropy systematics.…”

Section: Introductionmentioning

confidence: 99%

Gaussianity of Degree‐Scale Cosmic Microwave Background Anisotropy Observations

Park

Ratra

et al. 2001

ApJ

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We present results from a Ðrst test of the Gaussianity of degree-scale cosmic microwave background (CMB) anisotropy. We investigate Gaussianity of the CMB anisotropy by studying the topology of CMB anisotropy maps from the QMAP and Saskatoon experiments. We also study the QMASK map, a combination map of the QMAP and Saskatoon data. We measure the genus from noise-suppressed Wiener-Ðltered maps at an angular scale of aboutTo test the Gaussianity of the observed anisot-1¡ .5. ropy, we compare these results to those derived from a collection of simulated maps for each experiment in a Gaussian spatially Ñat, cosmological constant dominated, cold dark matter model. The genusÈ threshold level relations of the QMAP and Saskatoon maps are consistent with Gaussianity. While the combination QMASK map has a mildly non-Gaussian genus curve that is not a consequence of known foreground contamination, this result is not statistically signiÐcant at the 2 p level. These results extend previous upper limits on the non-Gaussianity of the large angular scale ([10¡) CMB anisotropy (measured by the COBE Di †erential Microwave Radiometer experiment) down to degree angular scales.

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Section: Introductionmentioning

confidence: 99%

Gaussianity of Degree‐Scale Cosmic Microwave Background Anisotropy Observations

Park

Ratra

et al. 2001

ApJ

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“…Furthermore, it gives smaller numbers of coefficients within each sub-band for the analysis. We instead use the dyadic decomposition to avoid these two weaknesses, as in Aghanim et al (1998).…”

Section: Discussionmentioning

confidence: 99%

Searching for non-gaussianity: Statistical tests

Forni

Aghanim

1999

Astron. Astrophys. Suppl. Ser.

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Abstract. Non-gaussianity represents the statistical signature of physical processes such as turbulence. It can also be used as a powerful tool to discriminate between competing cosmological scenarios. A canonical analysis of non-gaussianity is based on the study of the distribution of the signal in the real (or direct) space (e.g. brightness, temperature).This work presents an image processing method in which we propose statistical tests to indicate and quantify the non-Gaussian nature of a signal. Our method is based on a wavelet analysis of a signal. Because the temperature or brightness distribution is a rather weak discriminator, the search for the statistical signature of non-gaussianity relies on the study of the coefficient distribution of an image in the wavelet decomposition basis which is much more sensitive.We develop two statistical tests for non-gaussianity. In order to test their reliability, we apply them to sets of test maps representing a combination of Gaussian and nonGaussian signals. We deliberately choose a signal with a weak non-Gaussian signature and we find that such a nonGaussian signature is easily detected using our statistical discriminators. In a second paper, we apply the tests in a cosmological context.

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“…This effect (hereafter the BG effect) has garnered attention largely in the context of galaxy clusters moving across the sky, inducing secondary anisotropies in the CMB brightness temperature (Birkinshaw & Gull 1983; Birkinshaw 1989; Aghanim et al 1998). 3 The influence of cluster lens transverse motion on weakly and strongly lensed background galaxies has also been investigated (Molnar & Birkinshaw 2003).…”

Section: Transverse Moving Lensesmentioning

confidence: 99%

Lyα absorbers in motion: consequences of gravitational lensing for the cosmological redshift drift experiment★

Killedar

Lewis

2009

Monthly Notices of the Royal Astronomical Society

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The evolution of the expansion rate of the Universe results in a drift in the redshift of distant sources over time. A measurement of this drift would provide us with a direct probe of expansion history. The Lyman α (Lyα) forest has been recognized as the best candidate for this experiment, but the signal would be weak and it will take next generation large telescopes coupled with ultrastable high‐resolution spectrographs to reach the cm s−1 resolution required. One source of noise that has not yet been assessed is the transverse motion of Lyα absorbers, which varies the gravitational potential in the line of sight and subsequently shifts the positions of background absorption lines. We examine the relationship between the pure cosmic signal and the observed redshift drift in the presence of moving Lyα clouds, particularly the collapsed structures associated with Lyman limit systems and damped Lyα systems. Surprisingly, the peculiar velocities and peculiar accelerations both enter the expression, although the acceleration term stands alone as an absolute error, whilst the velocity term appears as a fractional noise component. An estimate of the magnitude of the noise reassures us that the motion of the Lyα absorbers will not pose a threat to the detection of the signal.

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Using the COBE/DMR data as a test-bed for normality assessments

Cited by 35 publications

References 19 publications

Gaussianity of Degree‐Scale Cosmic Microwave Background Anisotropy Observations

Gaussianity of Degree‐Scale Cosmic Microwave Background Anisotropy Observations

Searching for non-gaussianity: Statistical tests

Lyα absorbers in motion: consequences of gravitational lensing for the cosmological redshift drift experiment★

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