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Abstract: The optical spectra of objects classified as QSOs in the SDSS DR6 areanalyzed with the aim of determining the value of the fine structure constantin the past and then check for possible changes in the constant overcosmological timescales. The analysis is done by measuring the position of thefine structure lines of the OIII doublet 4959 and 5008 in QSO nebularemission. From the sample of QSOs at redshifts z < 0.8 a subsample was selectedon the basis of the amplitude and width of the OIII lines. Two differentmethod were used to determine the position of the lines of the OIII doublet,both giving similar results. Using a clean sample containing 1568 of suchspectra, a value of Delta alpha -alpha=+2.4 +-2.5 x 10^{-5} in the range ofredshifts 0-0.8 was determined. The use of a larger number of spectra allows afactor ~5 improvement on previous constraints based on the same method. On thewhole, we find no evidence of changes in alpha on such cosmological timescales.The mean variation compatible with our results is 1- Deltaalpha-alpha=+0.7 +- 0.7 x 10^{-14} yr^{-1}. The analysis was extended to theNeIII and SII doublets, although their usefulness is limited due to thefact that all these doublets in QSOs tend to be fainter than OIII, and thatsome of them are affected by systematics.



Author: C. M. Gutierrez, M. Lopez-Corredoira

Source: https://arxiv.org/







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