A&A 487, 63-74 (2008)

DOI: 10.1051/0004-6361:20077688

## Constraining dark energy via baryon acoustic oscillations in the (an)isotropic light-cone power spectrum

**C. Wagner, V. Müller, and M. Steinmetz**

AIP - Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

e-mail: cwagner@aip.de

Received 20 April 2007 / Accepted 15 May 2008

** Abstract ***Context. *The measurement of the scale of the baryon acoustic oscillations (BAO) in
the galaxy power spectrum as a function of redshift is a promising method to
constrain the equation-of-state parameter of the dark energy *w*.*Aims. *To measure the scale of the BAO precisely, a substantial volume of space must be surveyed. We test whether light-cone effects are important and
whether the scaling relations used to compensate for an incorrect reference
cosmology are in this case sufficiently accurate. We investigate the
degeneracies in the cosmological parameters and the benefits of
using the two-dimensional anisotropic power spectrum. Finally, we estimate
the uncertainty with which *w* can be measured by
proposed surveys at redshifts of about *z* = 3 and *z* = 1, respectively.*Methods. *Our data is generated by cosmological *N*-body simulations of the standard
CDM scenario. We construct galaxy catalogs by "observing" the
redshifts of different numbers of mock galaxies on a light cone at redshifts
of about *z* = 3 and *z* = 1. From the "observed" redshifts, we calculate the
distances, assuming a reference cosmology that depends on
. We do this for
= -0.8, -1.0, and -1.2 holding the other cosmological parameters
fixed. By fitting the corresponding (an)isotropic power spectra, we determine
the apparent scale of the BAO and the corresponding *w*.*Results. *In the simulated survey we find that light-cone effects are small and
that the simple scaling relations used to correct for the cosmological
distortion work fairly well even for large survey volumes.
The analysis of the two-dimensional anisotropic power spectra enables an
independent determination to be made of the apparent scale of the BAO, perpendicular and
parallel to the line of sight. This is essential for two-parameter *w*-models, such
as the redshift-dependent dark energy model
*w* = *w*_{0}+(1-*a*) *w*_{a}.
Using Planck priors for the matter and baryon density and
= 5% for the Hubble constant,
we estimate that the BAO measurements of future surveys
around *z* = 3 and *z* = 1 will be able to constrain, independently of other
cosmological probes, a constant *w* to ~12% and ~11% (68% c.l.), respectively.

**Key words:**cosmology: cosmological parameters

**--**cosmology: large-scale structure of Universe

**©**

*ESO 2008*