Robust dark energy constraints from supernovae, galaxy clustering, and 3 yr Wilkinson Microwave Anisotropy Probe observations

Type Ia supernova ( SN Ia), galaxy clustering, and cosmic microwave background ( CMB) anisotropy data provide complementary constraints on the nature of the dark energy in the universe. We find that the 3 yr Wilkinson Microwave Anisotropy Probe ( WMAP) observations give a CMB shift parameter of R (Omega H-m(0)2)(1/2)integral(zCMB)(0) dz'/H(z') = 1.70 +/- 0.03. Using this new measured value of the CMB shift parameter, together with the baryon acoustic oscillation ( BAO) measurement from the Sloan Digital Sky Survey ( SDSS), and SN Ia data from the HST/GOODS program and the first-year Supernova Legacy Survey, we derive model-independent constraints on the dark energy density rho(X) ( z) and the cosmic expansion rate H( z). We also derive constraints on the dark energy equation of state w(X) ( z) w(0) + w'z ( with cutoff at z 2) and w(X) ( a) w(0) + ( 1 - a) w(a). We find that current data provide slightly tighter constraints on rho(X) ( z) and H( z) as free functions in redshift and roughly a factor of 2 improvement in constraining w(X) ( z). A cosmological constant remains consistent with the data; however, uncertainties remain large for model-independent constraints of dark energy. A significant increase in the number of observed SNe Ia between redshifts of 1 and 2, complemented by improved BAO and weak-lensing cosmography measurements ( as expected from the JEDI mission concept for the Joint Dark Energy Mission), will be required to dramatically tighten model-independent dark energy constraints.