Presentasjon av masteroppgave: Max Grönke
Gravitational Redshift of Clusters in the Symmetron and Chameleon ƒ(R) Models
The gravitational redshift in clusters of galaxies can be measured to probe gravity as was first done by Wojtak et al. (2011). Using N -body simulations we are able to analyze the gravitational redshift profiles for the symmetron and the Hu-Sawicky ƒ(R) models. The characteristic feature of these models is the screening mechanism that hides the fifth force in dense environments recovering general relativity. We find that due to the nature of the screening, the deviation with respect to ΛCDM is highly dependent on the halo mass. So the ƒ(R) parameters |ƒR0 − 1| = 10−5, n = 1 cause an enhancement of the gravitational signal by up to 60% for halos with masses between 3 × 1012 M⊙h−1 and 1014 M⊙h−1.
However, for both larger and smaller halos there is hardly any deviation present. The characteristic mass range, where the fifth force is most active, varies with the model parameters. Additionally, we observe not only a stronger but also a possible weaker gravitational redshift. This contradicts the usual assumption that the presence of a fifth force leads to a deeper potential well but may happen if screening in the central regions is active which results in a shift of the additional clustering to larger radii.
Veileder: David F. Mota/Claudio Llinares
Intern sensor: Per B. Lilje
Ekstern sensor: Jose Beltran, Université Catholique de Louvain, Belgia