1202.5238 (Yun Wang)

Robust constraints on dark energy and gravity from galaxy clustering
data    [PDF]

Yun Wang

Galaxy clustering data provide a powerful probe of dark energy. We examine
how the constraints on the scaled expansion history of the universe,
x_h(z)=H(z)s (with s denoting the sound horizon at the drag epoch), and the
scaled angular diameter distance, x_d(z)=D_A(z)/s, depend on the methods used
to analyze the galaxy clustering data. We find that using the observed galaxy
power spectrum, P_g^{obs}(k), x_h(z) and x_d(z) are measured more accurately
and are significantly less correlated with each other, compared to using only
the information from the baryon acoustic oscillations (BAO) in P_g^{obs}(k).
Using the {x_h(z), x_d(z)} from P_g^{obs}(k) gives a DETF dark energy FoM
approximately a factor of two larger than using the {x_h(z), x_d(z)} from BAO
only; this provides a robust conservative method to go beyond BAO only in
extracting dark energy information from galaxy clustering data.
Furthermore, we find that if the redshift-space distortion information
contained in P_g^{obs}(k) is used, we can measure {x_h(z), x_d(z),
f_g(z)G(z)\tilde{P}_0^{1/2}/s^4} with high precision from a Stage IV galaxy
redshift survey with 0.7linear growth rate and linear growth factor of large scale structure
respectively, and \tilde{P}_0 is the dimensionless normalization of the linear
matter power spectrum. Adding f_g(z)G(z)\tilde{P}_0^{1/2}/s^4 to {x_h(z),
x_d(z)} significantly boosts the dark energy FoM, compared to using {x_h(z),
x_d(z)} only, or using P_g^{obs}(k) marginalized over the growth information,
assuming that gravity is not modified. Alternatively,
f_g(z)G(z)\tilde{P}_0^{1/2}/s^4 provides a powerful test of gravity.

View original: http://arxiv.org/abs/1202.5238