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Originally Posted by Nereid
Well, the authors themselves explain it, in the very same paragraph as the quote you selected!In short, the apparent periodicity arises from selection effect (the bane of an astronomer's life).
The Bell and McDiarmid paper is a valiant attempt to tease out a periodicity in the SDSS QSO z data, and address the Tang and Zhang analyses. I feel this second paper falls short of achieving its stated objective, not least because it addresses selection effects inadequately (I also think their statistical analyses are less robust than Tang and Zhang's, but haven't looked at it in sufficient detail to say for sure).
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Why do you give an opinion before looking at it in detail?
Bell et al. show that the total redshift distribution shows a peak at z=0.7 (just like Tang et al did) and subtract the smoothed distribution from the raw data (the reverse of a selection bias is also a "bane of an astronomer's life"). The resulting peaks are strongly supporting Bell's (and Burbidge's) equation that was beased on a specific example of 14 QSO's around NGC 1068.
Btw, shouldn't this be discussed in the Arp et al. thread?
Cheers.