all projects tagged CMB

CMB-lensing

2014

The fluctuation pattern of the temperature and polarisation of the cosmic microwave background gets distorted by weak lensing deflection and changes therefore its correlation properties. Our group is interested in higher-order effects in lensing and cross-correlations between the lensing effect and other probes of the cosmic large-scale structure. For small-scale CMB-lensing our cooperation partners are V.M. Böhm (Berkeley) and S. Hagstotz (Stockholm). From a methodical point of view closely related is the question of lensing of the 21cm background, which however involves more aspects of non-Gaussianity and reionisation history, including its non-uniformity.

integrated Sachs-Wolfe effect

2006

The iSW-effect is a secondary CMB-anisotropy and can be used to measure the equation of state of dark energy. Our results on the iSW-effect include the extension to nonlinearly evolving structures (Rees-Sciama-effect), the interpretation of the iSW-effect as a higher-order lensing phenomenon and cross-correlations with the weak lensing field. Using data from the European Planck-satellite, we have obtained independent measurements on the existence and properties of dark energy, in cooperation with P. Vielva (Santander) and C. Hernandez-Monteagudo (Teruel).

Planck

2005

The Planck-surveyor satellite was a European CMB-mission that mapped out the temperature and polarisation fluctuations to angular scales of a few arcminutes. We added Sunyaev-Zel’dovich simulations to the Planck-sky model, as well as adopting maps of the vibrational transitions of carbon monoxide and of the free-free-emission due to direct interaction between electrons. In analysing the data, we obtained independent information on dark energy from the measurement of the integrated Sachs-Wolfe effect (together with P. Vielva and C. Hernandez-Monteagudo).

Sunyaev-Zel'dovich-effect

2002

The Sunyaev-Zel’dovich effect describes a tiny transfer of thermal or kinetic energy from the hot intra-cluster medium of a galaxy cluster to the cold cosmic microwave background. It is a tool for detecting clusters of galaxies out to very high redshift, and provides a diagnostic of the relationship between temperature and mass of clusters. In addition, the kinetic Sunyaev-Zel’dovich effect arises due to a minuscule transfer of kinetic energy from the galaxy cluster’s electrons to the CMB photons, if the cluster is not at rest in a frame in which the CMB appears isotropic.