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Originally Posted by Ian
..."After smoothing off the sharp edges in the lowest and highest redshifts, a periodicity around Δz= 0.67 is detected in the full sample of SDSS QSOs, as shown in Fig. 9; however a periodicity of Δz= 0.67 ± 0.05 or any other frequency is not found in the 2dF QSOs, as shown in Fig. 10."
But conclude the section by writing:
"In sum, there is no evidence for intrinsic periodicity in redshifts of QSOs."
Can anyone help explain why the sum is no periodicity, even though they found a periodicity?
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Originally Posted by Nereid
Well, the authors themselves explain it, in the very same paragraph as the quote you selected!
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Such a difference between these two surveys is not surprising since the redshift-dependent spectroscopic completeness is relatively flat in 2dF (Croom et al. 2004), while in SDSS the spectroscopic completeness varies drastically at some redshifts (Richards et al. 2002). It is therefore improper to use all QSO redshifts in SDSS to probe any intrinsic periodicity without addressing selection bias... As shown in Fig. 11, no periodicity is found in the high-completeness sample where the power spectrum is consistent with a continuously ascending curve due to the low frequency component of the redshift distribution, whereas in different low-completeness samples, strong periodicity always appears, but with different peak locations (0.88 in (b), 0.67 in (c) and 0.74 in (d)). This should be a strong indicator that the peaks in low-completeness samples are caused by different selection effects in different samples. In sum, there is no evidence for intrinsic periodicity in redshifts of QSOs.
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In short, the apparent periodicity arises from selection effect (the bane of an astronomer's life). |
Papers like this actually convinced me that the observation of periodicity in quasar distances most likely IS an artifact of selection bias, but in a way it is just begging the question:
Why is there the appearance of a periodic effect in an incomplete sample?
The Mainstream, John Keirein, and Jacques Moret-Bailly can all answer this question, although it is Jacques who first articulated the solution:
The Lyman Forest forms when light is redshifted throught the Lyman alpha, beta and gamma absorbing bands of the hydrogen spectra. Since these effects SHOULD be periodic with increasing distance if the intervening medium is roughly consistent, or statistically consistent on the greatest of scales. This means that there is a sudden dimming of the spectra at certain distances and that as these bands of spectral dimming over-lap each other, the periodic effects found by Bell should and do emerge at multiples of the Lyman frequencies.
The fact that incomplete cuts from the Sloan survey demonstrate periodic distributions in magnitude biased samples but not 'complete' samples is consistent with this explanation. Notice that the effect should be exhibited whether or not the quasar redshift is cosmic or local, as JMB and John Kierein argue. So which is it?
Accornding to the Mainstream argument, the Lyman Forest absorbing clouds are in very extended space about quasar systems, While both John and Jacques argue there is an intrinsic mechanism that rachets the Lyman forest very very close to the quasar galaxy.
The defining test of whether or not there is intrinsic factors is the transverse proximity effect:When high redshift quasars are 'nearly behind' low redshift quasars, a second iteration of the Lyman Forest should appear in the spectra of the high redshift quasars. Several studies have concluded this effect does not occur nulling this hypothesis, and the only reasonable answer is that some of the redshifting mechanism is contained within the galaxies themselves: Quasars and their galaxies are both intrinsically and cosmically redshifted.
This is also apparent in the Butcher-Oemler effect, which has also been confirmed in these large galaxy surveys: Young, often quasar containing galaxies are more likely to be 'field' rather than 'cluster' galaxies in local space, while with increasing distance they are more likely to be cluster-centered. This is also a periodic effect which is certainly not anticipated in any evolutionary scenario: Why would young galaxies suddenly hatch from clusters and speed off on there own? Again, the reasonable solution is to conclude there is an intrinsic, not periodic, redshifting that falsely catalogues near-by quasar galaxies as much more distant, artificially placing them in the distant 'field' rather than in closer clusters where they rightly belong.
I cannot fathom why mainstream researchers are so blind to the implications of these mainstream studies: This is not a case where new physics is required, only an acceptance that the long-held prejudice against non-Doppler mechanisms is blurrying their judgement:
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Originally Posted by James Burke - The Day the Universe Changed
...the philisophical viewpoint at the time of the resurgence of cities in the 10th and 11th centuries, left their citizens ill-prepared for the new problems demanding solutions. There was no concept of progress. In the early middle ages men were aware only of the greatness that had been lost. "We stand on the shoulders of giants", they said, "The past held all that was great and glorious. It was the source of all authority. The purpose of all intellectual activity was not to question this past world, but to add respect for it."
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How dare we say our science is complete! New observation should always trump old theories.