We present observational constraints on the nature of dark energy using the Supernova Legacy Survey three year sample ( SNLS3 ) of Guy et al .
( 31 ) and Conley et al .
( 16 ) .
We use the 472 SNe Ia in this sample , accounting for recently discovered correlations between SN Ia luminosity and host galaxy properties , and include the effects of all identified systematic uncertainties directly in the cosmological fits .
Combining the SNLS3 data with the full WMAP7 power spectrum , the Sloan Digital Sky Survey luminous red galaxy power spectrum , and a prior on the Hubble constant H _ { 0 } from SHOES , in a flat universe we find \Omega _ { m } = 0.269 \pm 0.015 and w = -1.061 ^ { +0.069 } _ { -0.068 } ( where the uncertainties include all statistical and SN Ia systematic errors ) – a 6.5 % measure of the dark energy equation-of-state parameter w .
The statistical and systematic uncertainties are approximately equal , with the systematic uncertainties dominated by the photometric calibration of the SN Ia fluxes – without these calibration effects , systematics contribute only a \sim 2 % error in w .
When relaxing the assumption of flatness , we find \Omega _ { m } = 0.271 \pm 0.015 , \Omega _ { k } = -0.002 \pm 0.006 , and w = -1.069 ^ { +0.091 } _ { -0.092 } .
Parameterizing the time evolution of w as w ( a ) = w _ { 0 } + w _ { a } ( 1 - a ) , gives w _ { 0 } = -0.905 \pm 0.196 , w _ { a } = -0.984 ^ { +1.094 } _ { -1.097 } in a flat universe .
All of our results are consistent with a flat , w = -1 universe .

The size of the SNLS3 sample allows various tests to be performed with the SNe segregated according to their light curve and host galaxy properties .
We find that the cosmological constraints derived from these different sub-samples are consistent .
There is evidence that the coefficient , \beta , relating SN Ia luminosity and color , varies with host parameters at > 4 \sigma significance ( in addition to the known SN luminosity–host relation ) ; however this has only a small effect on the cosmological results and is currently a sub-dominant systematic .