156 research outputs found
Non-Gaussianity of the Cosmic Infrared Background anisotropies II : Predictions of the bispectrum and constraints forecast
Using a full analytical computation of the bispectrum based on the halo model
together with the halo occupation number, we derive the bispectrum of the cos-
mic infrared background (CIB) anisotropies that trace the clustering of
dusty-star- forming galaxies. We focus our analysis on wavelengths in the
far-infrared and the sub-millimeter typical of the Planck/HFI and
Herschel/SPIRE instruments, 350, 550, 850, and 1380 um. We explore the
bispectrum behaviour as a function of several models of evolution of galaxies
and show that it is strongly sensitive to that ingredient. Contrary to the
power spectrum, the bispectrum, at the four wavelengths, seems dominated by low
redshift galaxies. Such a contribution can be hardly limited by applying low
flux cuts. We also discuss the contributions of halo mass as a function of the
redshift and the wavelength, recovering that each term is sensitive to a
different mass range. Furthermore, we show that the CIB bispectrum is a strong
contaminant of the Cosmic Microwave Background bispectrum at 850 um and higher.
Finally, a Fisher analysis of the power spectrum, bispectrum alone and of the
combination of both shows that degeneracies on the HOD parameters are broken by
including the bispectrum information, leading to tight constraints even when
including foreground residuals.Comment: 16 pages, Accepted by MNRA
Non-Gaussianity of the Cosmic Infrared Background anisotropies I : Diagrammatic formalism and application to the angular bispectrum
We present the first halo model based description of the Cosmic Infrared
Background (CIB) non-Gaussianity (NG) that is fully parametric. To this end, we
introduce, for the first time, a diagrammatic method to compute high order
polyspectra of the 3D galaxy density field. It allows an easy derivation and
visualisation of the different terms of the polyspectrum. We apply this
framework to the power spectrum and bispectrum, and we show how to project them
on the celestial sphere in the purpose of the application to the CIB angular
anisotropies. Furthermore, we show how to take into account the particular case
of the shot noise terms in that framework. Eventually, we compute the CIB
angular bispectrum at 857 GHz and study its scale and configuration
dependencies, as well as its variations with the halo occupation distribution
parameters. Compared to a previously proposed empirical prescription, such
physically motivated model is required to describe fully the CIB anisotropies
bispectrum. Finally, we compare the CIB bispectrum with the bispectra of other
signals potentially present at microwave frequencies, which hints that
detection of CIB NG should be possible above 220 GHz.Comment: 21 pages, 21 figures. Accepted by MNRA
The distance duality relation from X-ray and SZ observations of clusters
X-ray and Sunyaev-Zel'dovich data of clusters of galaxies enable to construct
a test of the distance duality relation between the angular and luminosity
distances. We argue that such a test on large cluster samples may be of
importance while trying to distinguish between various models of dark energy.
The analysis of a data set of 18 clusters shows no significant violation of
this relation. The origin and amplitude of systematic effects and the
possibility to increase the precision of this method are discussed.Comment: RevTex, 7 pages, 6 figure
A new parameterization of the reionisation history
Motivated by the current constraints on the epoch of reionisation from recent
cosmic microwave background observations, ionising background measurements of
star-forming galaxies, and low redshifts line-of-sight probes, we propose a new
data-motivated parameterisation of the history of the average ionisation
fraction. This parameterisation describes a flexible redshift-asymmetric
reionisation process in two regimes that is capable of fitting all the current
constraints.Comment: 5 page
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