Topic001: Discussion on Redshift Magnitude Bands, Bill Tifft 11/12/14
QTC really seriously began with the discovery of Redshift-Magnitude Bands in the Coma cluster of galaxies. For light the redshift (or blueshift) is a frequency shift seen in spectral features which can be caused several ways. Interpreted as due to motion (a Doppler shift) it is conveniently expressed as a velocity, V, or in dimensionless units z=V/c where c is the speed of light. I will use both V and z for convenience only, leaving interpretation of what really causes the shift open for discussion. The redshift is just an observable quantity at this point of discussion, the ultimate issue here is what really is the cosmic redshift?
The magnitude of a galaxy is just a measure of how much energy is being emitted into space, and how far away the galaxy is. There is little doubt about what magnitude means. There are different types of magnitudes, measures in different parts of the spectrum or different parts of the galaxy. The initial magnitudes I used corresponded with a specific nuclear region (a 4.8 arc second spot centered on the nucleus) in the visual (V=yellow) portion of the spectrum.
Now look at the upper left frame of Figure 1 in the ASP paper (or Figure 1.2 of my book), used as the lead figure in this topic. (For book information or acquisition see Post001 and Post002.) Does it look like there is any relationship between the magnitudes of the Coma galaxies in the core of the cluster and their redshifts? No assumptions now, remember we are just asking `what is the redshift?’ OK, so someone told you the redshift was a measure of motion which should have nothing to do with the magnitude of a galaxy. Well if that were the case the diagram should be a scatter diagram in redshift, representing the random motion of the galaxies within the cluster. Is it?
What about bias in the data? The photometry and redshifts were quickly confirmed, I have a reputation for generating data of excellent quality. The probability of such a banded pattern by accident was shown to be on the order of 0.0005 by itself and there are several other correlations involved. The elliptical galaxies (filled circles) have a significantly lower redshift than the later types (open circles), and that pattern applies along each band. (There will be much more about that later). Next, the lower left frame Figure 1 in the ASP paper shows that the bands converge toward zero. They appear to be scaled versions of one another (parallel in a log redshift plot). They are also quite precisely factors of two apart in brightness (3/4 of a magnitude).
When I presented the Coma cluster findings at the Amherst meeting of the American Astronomical Society in 1972 there was quite a reaction. A very well known astrophysicist debated the findings actively, but afterwards said he might think about it if I could show the effect in another cluster. I never heard back from him, and know of no other astronomer who has looked for such structure. The upper right figure in Figure 1 of the ASP paper shows the result for the A2199 cluster which I soon produced. The cluster is a perfect extension of the Coma study. The figure at lower right is a recent unpublished study by me of published work on the higher redshift cluster 1358+62. The authors say nothing about banding. All of this and more is covered in detail in the first twelve pages of Seminar 1 of my book. Any comments? Note that this is only the beginning, my book has 460 pages. I will say more about banding and its implications in Topic002, Banding, Substructure and Gravity. Now, 40+ years after the Coma findings I believe I understand what redshift-magnitude bands represent. There is much more to discuss first. Banding is discussed in Seminar 8, although I found the answer in Seminar 5 in the Hubble Deep Field.
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