Cosmology with clusters of galaxies and their SZ signal

par Mlle Barbara Comis (LPSC)

mardi 23 févr. 2016, 14:00 → 15:00 Europe/Paris

CPPM

As the last step of the hierarchical structure formation process, clusters of galaxies represent the largest gravitationally bound objects that we can observe in our Universe. Since they formed all along the cosmic history, they contain plenty of information about the evolution of the Universe, and can then provide a strong tool for cosmological investigation, complementary to CMB. Most of the cluster baryons are present as a diffuse gas, the Intra-Cluster Medium (ICM), which is hot (106 - 108 K) and completely ionized. At these temperatures the ICM electrons Compton inverse interact with CMB photons producing the thermal Sunyaev-Zel’dovich (SZ) effect (a distortion of the CMB spectrum at the cluster position). In the last years survey dedicated instruments (Planck, ACT, SPT) have finally been able to produce SZ selected catalogues containing several hundreds of clusters. And in fact clusters and their SZ signal are becoming increasingly used to derive cosmological constraints. However, cluster derived cosmology is limited by our ability to translate cluster observables into mass estimates and tracers of the matter distribution. Then, a thorough study of the scatter that the details of cluster morphology and astrophysics might introduce around the average observable-to-mass behaviour is mandatory. This kind of study needs SZ observations with sub-arcminute angular resolution, such as those produced by the NIKA camera, working at the IRAM 30 m telescope. As a member of both the Planck and the NIKA collaborations, I will present the recent SZ results that both instruments have produced and will produce, with the final instrument NIKA2. In particular, I will discuss how their complementarity, especially in terms of angular resolution, can be used to address the systematics that currently limit cluster(SZ)-derived cosmology.