Gravitational Redshift from Galaxy Clusters

Fig. 1: The distributions of dark matter around galaxy clusters and their associated landscape of gravitational potential from N-body simulations. Top panels: distributions of dark matter within a 10 Mpc/h radius of the simulated galaxy clusters at the centres. The colour displays the relative density of dark matter. Middle panels: The same regions and colour coding as the top panels but now showing the value of the gravitational potential on the y-axis. The central clusters induce deep potential wells; substructures and neighbouring structures generate local potential minima. Photons from central galaxies sitting at the bottom of the potential well of galaxy clusters are expected to be gravitationally redshifted by a larger amount than satellites and other neighbouring galaxies. The difference of the gravitational redshift signal with respect to the cluster centre is of the order of 10 km/s. It can in principle be detected by stacking a large sample of clusters. (Cai et al. 2016).