Calibrating the cosmic distance scale ladder: the role of the sound
  horizon scale and the local expansion rate as distance anchors
  We exploit cosmological-model independent measurements of the expansion
history of the Universe to provide a cosmic distance ladder. These are
supernovae type Ia used as standard candles (at redshift between 0.01 and 1.3)
and baryon acoustic oscillations (at redshifts between 0.1 and 0.8) as standard
rulers. We calibrate (anchor) the ladder in two ways: first using the local
$H_0$ value as an anchor at $z$ = 0 (effectively calibrating the standard
candles) and secondly using the cosmic microwave background-inferred
sound-horizon scale as an anchor (giving the standard ruler length) as an
inverse distance ladder. Both methods are consistent, but the uncertainty in
the expansion history $H(z)$ is smaller if the sound horizon scale is used. We
present inferred values for the sound horizon at radiation drag $r_d$ which do
not rely on assumptions about the early expansion history nor on cosmic
microwave background measurements but on the cosmic distance ladder and baryon
acoustic oscillations measurements. We also present derived values of $H_0$
from the inverse distance ladder and we show that they are in very good
agreement with the extrapolated value in a $\Lambda$CDM model from Planck
cosmic microwave background data.
