We compare the dark energy model constraints obtained by using recent standard ruler data ( Baryon Acoustic Oscillations ( BAO ) at z = 0.2 and z = 0.35 and Cosmic Microwave Background ( CMB ) shift parameters R and l _ { a } ) with the corresponding constraints obtained by using recent Type Ia Supernovae ( SnIa ) standard candle data ( ESSENCE+SNLS+HST from astro-ph/0701510 ) .
We find that , even though both classes of data are consistent with \Lambda CDM at the 2 \sigma level , there is a systematic difference between the two classes of data .
In particular , we find that for practically all values of the parameters ( \Omega _ { 0 m } , \Omega _ { b } ) in the 2 \sigma range of the the 3-year WMAP data ( WMAP3 ) best fit , \Lambda CDM is significantly more consistent with the SnIa data than with the CMB+BAO data .
For example for ( \Omega _ { 0 m } , \Omega _ { b } ) = ( 0.24 , 0.042 ) corresponding to the best fit values of WMAP3 , the dark energy equation of state parametrization w ( z ) = w _ { 0 } + w _ { 1 } \frac { z } { 1 + z } best fit is at a 0.5 \sigma distance from \Lambda CDM ( w _ { 0 } = -1 ,w _ { 1 } = 0 ) using the SnIa data and 1.7 \sigma away from \Lambda CDM using the CMB+BAO data .
There is a similar trend in the earlier data ( SNLS vs CMB+BAO at z = 0.35 ) .
This trend is such that the standard ruler CMB+BAO data show a mild preference for crossing of the phantom divide line w = -1 , while the recent SnIa data favor \Lambda CDM .
Despite of this mild difference in trends , we find no statistically significant evidence for violation of the cosmic distance duality relation \eta \equiv \frac { d _ { L } ( z ) } { d _ { A } ( z ) ( 1 + z ) ^ { 2 } } = 1 .
For example , using a prior of \Omega _ { 0 m } = 0.24 , we find \eta = 0.95 \pm 0.025 in the redshift range 0 < z < 2 , which is consistent with distance duality at the 2 \sigma level .