First Cosmological Constraints on Dark Energy from the Radial Baryon Acoustic Scale

We present cosmological constraints arising from the first measurement of the radial (line-of-sight) baryon acoustic oscillations (BAO) scale in the large scale structure traced by the galaxy distribution. Here we use these radial BAO measurements at $z=0.24$ and $z=0.43$ to derive new constraints on dark energy and its equation of state for a flat universe, without any other assumptions on the cosmological model: $w=\ensuremath{-}1.14\ifmmode\pm\else\textpm\fi{}0.39$ (assumed constant), ${\ensuremath{\Omega}}_{m}={0.24}_{\ensuremath{-}0.05}^{+0.06}$. If we drop the assumption of flatness and include previous cosmic microwave background and supernova data, we find $w=\ensuremath{-}0.974\ifmmode\pm\else\textpm\fi{}0.058$, ${\ensuremath{\Omega}}_{m}=0.271\ifmmode\pm\else\textpm\fi{}0.015$, and ${\ensuremath{\Omega}}_{k}=\ensuremath{-}0.002\ifmmode\pm\else\textpm\fi{}0.006$, in good agreement with a flat cold dark matter cosmology with a cosmological constant. To our knowledge, these are the most stringent constraints on these parameters to date under our stated assumptions.

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