Why does the peak of quasar distribution move from near to far with increasing magnitude? #210
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GN-z11 has an estimated absolute magnitude of -22.1. https://iopscience.iop.org/article/1...637X/819/2/129 If we can see galaxies of that magnitude at z=11... surely quasars of that magnitude should be detectable as well? But the population of quasars of that magnitude doesn't exist at z > 1.6. Here is what I suspect. 1. K-correctionsThe K-corrections used are from 2006. Richards, et al: https://ui.adsabs.harvard.edu/abs/2006AJ....131.2766R/abstract Page 45: This is where things get really weird. The DR16 paper says this:
https://ui.adsabs.harvard.edu/abs/2020ApJS..250....8L/abstract Since the Richards table includes both emission line and continuum, and it's the same table used for all the data releases, how is that even possible? They would have had to explicitly remove the emission lines. Here is the code to generate DR16Q: https://github.com/bradlyke/dr16q/blob/master/abs_mag.py But there really is no way they would have only applied the continuum and not the emission lines. Unless the continuum was applied further up the pipeline in DR12. Which means there's a possibility "fixing" it in DR16, by applying the K-corrections, double dips the continuum. This might explain why low-z get assign dimmer magnitudes and high-z are calculated to be brighter. That's assuming the almost 20 year old table is even accurate. 2. Cosmological parametersThe bug report for DR12 also says the wrong parameters were used, and that's fixed, but they don't say what the old parameters were. Line 125 is this:
Here they are using the CMB (z~1100) measurement of Hubble's constant, 67.6, and applying this to the 0 < z < 5. Wouldn't it make more sense to use the value of Hubble's constant measured by supernovae in that range? That's a small thing. But on top of the K-corrections, it forces magnitudes to be a little brighter than they should be too. 3. False readingsAnother suspicion is that the brighter than -25 quasars are false readings. These videos explain that some of the brightest, when examined, are actually:
https://youtu.be/FCLv6W-D5hY?si=w-eBHo-70FXN2qkv&t=410 When we examine individual quasars closely... they turn out to be more than quasars. Aside: z > 5Line 142 of that code has this.
Basically since this 2006 table only goes up to z ~ 5, anything z > 5 is simply omitted from the dataset. Does anyone know that's actually there? It doesn't seem to be disclosed anywhere. It took me actually contacting SDSS to find the code for this. It took even them a few days to find the GitHub repo. |
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Using the DESI survey, and applying my bins (which represent equal volumes in non-expanding space) it seems the bright galaxy survey objects (BGS) jumps up exactly where the quasars fall off. This is at z=1.6, the alleged angular diameter turnaround. Maybe that has something to do with it. |
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I can't easily navigate your panels and some of them don't display well. However, assuming everything is fine with your data, I think your basic question can be answered using the idea of an intrinsic quasar redshift which scales with the magnitude. A model which illustrates this possibility was given by Hansen: https://arxiv.org/abs/1506.08784 The idea of an intrinsic quasar redshift was proposed much earlier by Arp and others, to account for the high redshift quasar being attached to a lower redshift galaxy. A number of mechanisms have been proposed for the quasar intrinsic redshift. Hansen attributes the redshift to an effect of light moving through a dense plasma. While his mechanism might not be correct, there are several important aspects of it which relate to your question. First, the idea that the intrinsic quasar redshift is a plasma effect is compatible with a redshift which scales with quasar magnitude: more plasma = more redshift. Images of nearby supermassive black holes (or AGNs) show them to be essentially rings of plasma and so quasar phenomena associated with such AGNs would be related to their size. Secondly, when more than one redshift is present, you can't just add the redshifts together. Instead, you have to multiply them, as in Eq. 3 of Hansen's paper. (This was emphasized by Arp also.) Thus, if we write the combined redshift as z3, the Hubble redshift as z1 and the intrinsic quasar redshift as z2, the corrected redshift is: (1 + z3) = (1 + z1) (1 + z2) , which gives z3 = z1 + z2 + z1z2 Now in Fig. 4 of Hansen's paper, he shows the intrinsic quasar redshifts ranging from roughly 0.1 to 1. Let's calculate the combined redshift for a .1 redshift quasar and a 1.0 redshift quasar for two separate Hubble redshifts, 0 and 1. For the quasar type with z2 = .1 and z1 = 0 we have the combined redshift z3 = 0 + .1 + 0 = .1 For the same quasar type at z1 = 1, we have a combined redshift z3 = 1 + .1 + .1 = 1.2. The peak will have shifted just a slight amount from the point where we just added the redshifts. The situation changes markedly for the quasar type with z2 = 1.0. For these quasars, if z1 = 0, we have z3 = 0 + 1 + 0 = 1. If z1 = 1, we have z3 = 1 + 1 + 1 = 3 ! To sum up, the low magnitude quasars for a Hubble redshift range of 0-1.0 are shifted to a range of .1-1.2. This is just a small change. But the high magnitude quasars will have been shifted to a range of 1-3, a large change. You mentioned that bright quasars stopped existing recently. From the above considerations, this might not be so. We don't see them at low redshift because the intrinsic redshift moves them out to a higher redshift. We would tend to see only the low magnitude quasars at very low redshifts. |
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Your little tool is wonderful @mikehelland ! There is a lot to unpack here. Some quick comments:
By sheer coincidence, the evolution (according to the BB model) of a complex system such as a quasar happens to follow a simple function of the redshift. Another coincidence that shows the Big Bang model cannot be correct. |
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@budrap00 some comments don't seem to add up. "A quasar can be thought of as the end product of a gravitational collapse." The computation of redshift I don't get. It's counter-intuitive. Please explain if there are specific mechanisms at play here? As that evolution proceeds, the total mass-energy of the quasar increases (via gravitational attraction/infall)
in proportion to the surface area which is growing
as while the mass-energy density decreases because the volume is increasing as ,
which results in a diminishing intrinsic redshift.
If a collapsing object (e.g the proposed quasar) is already a GR object, then adding mass will not reduce the density, even if the added mass is very low density. Electron degeneracy has already set in, else it is nowhere near a GR object. So the new mass will not lie on the surface like a fluffy cloud. An increase in mass still results in an increase in redshift, not a diminishing redshift. |
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Yes Bud, I deleted it. It was a rather thoughtless reply. Han
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I made a little tool to examine the distribution of quasars in various catalogs, including SDSS DR16Q:
https://mikehelland.github.io/hubbles-law/other/sdss.htm
If you check the +/- box, and move the magnitude slider from low (-20) to high (-30), the peak of the quasars moves from z=0 to about z=3.3.
Here's the results summarized:
One obvious factor is that the quasars on the dimmer end won't show up at high-z, simply because they're too dim. And very bright quasars ceased to exist recently.
But can that really explain this picture?
Is there something else going on? Seems odd the peak would move so linearly with magnitude.
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