We present the cosmological analysis of 752 photometrically–classified Type Ia Supernovae ( SNe Ia ) obtained from the full Sloan Digital Sky Survey II ( SDSS-II ) Supernova ( SN ) Survey , supplemented with host–galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey ( BOSS ) .
Our photometric–classification method is based on the SN typing technique of Sako et al .
( 128 ) , aided by host galaxy redshifts ( 0.05 < z < 0.55 ) .
SNANA simulations of our methodology estimate that we have a SN Ia typing efficiency of 70.8 % , with only 3.9 % contamination from core-collapse ( non-Ia ) SNe .
We demonstrate that this level of contamination has no effect on our cosmological constraints .
We quantify and correct for our selection effects ( e.g. , Malmquist bias ) using simulations .
When fitting to a flat \Lambda CDM cosmological model , we find that our photometric sample alone gives \Omega _ { m } = 0.24 ^ { +0.07 } _ { -0.05 } ( statistical errors only ) .
If we relax the constraint on flatness , then our sample provides competitive joint statistical constraints on \Omega _ { m } and \Omega _ { \Lambda } , comparable to those derived from the spectroscopically-confirmed three-year Supernova Legacy Survey ( SNLS3 ) .
Using only our data , the statistics–only result favors an accelerating universe at 99.96 % confidence .
Assuming a constant w CDM cosmological model , and combining with H _ { 0 } , CMB and LRG data , we obtain w = -0.96 ^ { +0.10 } _ { -0.10 } , \Omega _ { m } = 0.29 ^ { +0.02 } _ { -0.02 } and \Omega _ { k } = 0.00 ^ { +0.03 } _ { -0.02 } ( statistical errors only ) , which is competitive with similar spectroscopically confirmed SNe Ia analyses .
Overall this comparison is reÐassuring , considering the lower redshift leverage of the SDSS-II SN sample ( z < 0.55 ) and the lack of spectroscopic confirmation used herein .
These results demonstrate the potential of photometrically–classified SNe Ia samples in improving cosmological constraints .