We derive the escape velocity profile for an Einasto density field in an accelerating universe and demonstrate its physical viability by comparing theoretical expectations to both light-cone data generated from N-body simulations and archival data on 20 galaxy clusters. We demonstrate that the projection function (g(β)) is deemed physically viable only for the theoretical expectation that includes a cosmology-dependent term. Using simulations, we show that the inferred velocity anisotropy is more than 6{\sigma} away from the expected value for the theoretical profile that ignores the acceleration of the universe. In the archival data, we constrain the average velocity anisotropy parameter of a sample of 20 clusters to be β=0.248−0.360+0.164 at the 68% confidence level. Lastly, we briefly discuss how our analytic model may be used as a novel cosmological probe based on galaxy clusters.
@article{arxiv.1611.05816,
title = {On Escaping a Galaxy Cluster in an Accelerating Universe},
author = {Alejo Stark and Christopher J. Miller and Daniel Gifford},
journal= {arXiv preprint arXiv:1611.05816},
year = {2016}
}