47 research outputs found
Detecting Sunyaev-Zel'dovich clusters with PLANCK: III. Properties of the expected SZ-cluster sample
The PLANCK-mission is the most sensitive all-sky submillimetric mission
currently being planned and prepared. Special emphasis is given to the
observation of clusters of galaxies by their thermal Sunyaev-Zel'dovich (SZ)
effect. In this work, the results of a simulation are presented that combines
all-sky maps of the thermal and kinetic SZ-effect with cosmic microwave
background (CMB) fluctuations, Galactic foregrounds (synchrotron emission,
thermal emission from dust, free-free emission and rotational transitions of
carbon monoxide molecules) and sub-millimetric emission from planets and
asteroids of the Solar System. Observational issues, such as PLANCKs beam
shapes, frequency response and spatially non-uniform instrumental noise have
been incorporated. Matched and scale-adaptive multi-frequency filtering schemes
have been extended to spherical coordinates and are now applied to the data
sets in order to isolate and amplify the weak thermal SZ-signal. The properties
of the resulting SZ-cluster sample are characterised in detail: Apart from the
number of clusters as a function of cluster parameters such as redshift z and
total mass M, the distribution n(sigma)d sigma of the detection significance
sigma, the number of detectable clusters in relation to the model cluster
parameters entering the filter construction, the position accuracy of an
SZ-detection and the cluster number density as a function of ecliptic latitude
beta is examined.Comment: 14 pages, 16 figures, 13 tables, submitted to MNRAS, 16.Feb.200
Gravitational lensing of the cosmic microwave background by nonlinear structures
Weak gravitational lensing changes the angular power spectra of the cosmic
microwave background (CMB) temperature and polarization in a characteristic way
containing valuable information for cosmological parameter estimation and weak
lensing reconstructions. So far, analytical expressions for the lensed CMB
power spectra assume the probability density function (PDF) of the lensing
excursion angle to be Gaussian. However, coherent light deflection by nonlinear
structures at low redshifts causes deviations from a pure Gaussian PDF. Working
in the flat-sky limit we develop a method for computing the lensed CMB power
spectra which takes these non-Gaussian features into account. Our method does
not assume any specific PDF but uses instead an expansion of the characteristic
function of the lensing excursion angle into its moments. Measuring these in
the CMB lensing deflection field obtained from the Millennium Simulation we
show that the change in the lensed power spectra is only at the 0.1% - 0.4%
level on very small scales (below 4 arcmin) and demonstrate that the assumption
of a Gaussian lensing excursion angle PDF is well applicable.Comment: 9 pages, 2 figures, submitted to MNRA