The gravitational field of X-COP galaxy clusters
  The mass profiles of massive dark matter halos are highly sensitive to the
nature of dark matter and potential modifications of the theory of gravity on
large scales. The $\Lambda$CDM paradigm makes strong predictions on the shape
of dark matter halos and on the dependence of the shape parameters on halo
mass, such that any deviation from the predicted universal shape would have
important implications for the fundamental properties of dark matter. Here we
use a set of 12 galaxy clusters with available deep X-ray and Sunyaev-Zeldovich
data to constrain the shape of the gravitational field with an unprecedented
level of precision over two decades in radius. On average, we find that the NFW
profile provides an excellent description of the recovered mass profiles, with
deviations of less than 10% over a wide radial range. However, there appears to
be more diversity in the shape of individual profiles than can be captured by
the NFW model. The average NFW concentration and its scatter agree very well
with the prediction of the $\Lambda$CDM framework. For a subset of systems, we
disentangle the gravitational field into the contribution of baryonic
components (gas, brightest cluster galaxy, and satellite galaxies) and that of
dark matter. The stellar content dominates the gravitational field inside
$\sim0.02R_{500}$ but is responsible for only 1-2% of the total gravitational
field inside $R_{200}$. The total baryon fraction reaches the cosmic value at
$R_{200}$ and slightly exceeds it beyond this point, possibly indicating a mild
level of nonthermal pressure support ($10-20\%$) in cluster outskirts. Finally,
the relation between observed and baryonic acceleration exhibits a complex
shape that strongly departs from the radial acceleration relation in spiral
galaxies, which shows that the aforementioned relation does not hold at the
galaxy-cluster scale.
