Constraining the variation in the fine-structure constant using SDSS DR7 quasi-stellar object spectra
We report a robust constrain on the possible variation of fine -structure constant,α � e 2 /~c, obtained using Oiii λλ 4959,5007 nebular emission lines from QSOs.We find a �α/α = (2.1 ± 1.6) × 10 5 based on a well selected sample of 2347 QSOs from Sloan Digital Sky Survey Data Release 8 with 0.02< z< 0.74. Our result is consistent with a non-varyingα at a level of 2 × 10 5 over approximately 7 Gyr. This is the largest sample of extragalactic objects yet used to constrain the variation ofα. While this constraint is not as stringent as those determined using many-multiplet method it is free from various systematic effects. A factor of � 4 improvement in�α/α achieved here compared to the previous study (Bahcall et al. 2004) is just consistent with what is expected based on a factor of 14 times bigger sample used here. This suggests that errors are mainly dominated by the statistical uncertainty. We also find the ratio of transition probabilities corresponding to the Oiiiλ5007 andλ4959 lines to be 2.933±0.002, in good agreement with the National Institute of Standards and Technology measurements.