Model Independent Expansion History from Supernovae: Cosmology versus
  Systematics
  We examine the Pantheon supernovae distance data compilation in a model
independent analysis to test the validity of cosmic history reconstructions
beyond the concordance $\Lambda$CDM cosmology. Strong deviations are allowed by
the data at $z\gtrsim1$ in the reconstructed Hubble parameter, $Om$ diagnostic,
and dark energy equation of state. We explore three interpretations: 1)
possibility of the true cosmology being far from $\Lambda$CDM, 2) supernovae
property evolution, and 3) survey selection effects. The strong (and
theoretically problematic) deviations at $z\gtrsim1$ vanish and good
consistency with $\Lambda$CDM is found with a simple Malmquist-like linear
correction. The adjusted data is robust against the model independent iterative
smoothing reconstruction. However, we caution that while by eye the original
deviation from $\Lambda$CDM is striking, $\chi^2$ tests do not show the extra
linear correction parameter is statistically significant, and a
model-independent Gaussian Process regression does not find significant
evidence for the need for correction at high-redshifts.
