The observational status of Galileon gravity after Planck
  We use the latest CMB data from Planck, together with BAO measurements, to
constrain the full parameter space of Galileon gravity. We constrain separately
the three main branches of the theory known as the Cubic, Quartic and Quintic
models, and find that all yield a very good fit to these data. Unlike in
$\Lambda{\rm CDM}$, the Galileon model constraints are compatible with local
determinations of the Hubble parameter and predict nonzero neutrino masses at
over $5\sigma$ significance. We also identify that the low-$l$ part of the CMB
lensing spectrum may be able to distinguish between $\Lambda{\rm CDM}$ and
Galileon models. In the Cubic model, the lensing potential deepens at late
times on sub-horizon scales, which is at odds with the current observational
suggestion of a positive ISW effect. Compared to $\Lambda$CDM, the Quartic and
Quintic models predict less ISW power in the low-$l$ region of the CMB
temperature spectrum, and as such are slightly preferred by the Planck data. We
illustrate that residual local modifications to gravity in the Quartic and
Quintic models may render the Cubic model as the only branch of Galileon
gravity that passes Solar System tests.
