Iron in X-COP: tracing enrichment in cluster outskirts with high
  accuracy abundance profiles
  We present the first metal abundance profiles for a representative sample of
massive clusters. Our measures extend to $R_{500}$ and are corrected for a
systematic error plaguing previous outskirt estimates. Our profiles flatten out
at large radii, admittedly not a new result, however the radial range and
representative nature of our sample extends its import well beyond previous
findings. We find no evidence of segregation between cool-core and
non-cool-core systems beyond $\sim 0.3 R_{500}$, implying that, as was found
for thermodynamic properties (Ghirardini et al, 2019), the physical state of
the core does not affect global cluster properties. Our mean abundance within
$R_{500}$ shows a very modest scatter, $< $15%, suggesting the enrichment
process must be quite similar in all these massive systems. This is a new
finding and has significant implications on feedback processes. Together with
results from thermodynamic properties presented in a previous X-COP paper, it
affords a coherent picture where feedback effects do not vary significantly
from one system to another. By combing ICM with stellar measurements we have
found the amount of Fe diffused in the ICM to be about ten times higher than
that locked in stars. Although our estimates suggest, with some strength, that
the measured iron mass in clusters is well in excess of the predicted one,
systematic errors prevent us from making a definitive statement. Further
advancements will only be possible when systematic uncertainties, principally
those associated to stellar masses, both within and beyond $R_{500}$, can be
reduced.
