Dear Nereid and Phobos (seat belt on) can we talk about redshifts?

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  • #76
turbo
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Nereid said:
Thank you Chronos, a most interesting read.

This paper should allow us to put several 'association' and 'quantized z' hypotheses to sleep. Does anyone know if any serious astronomers in either of those camps are still banging those drums?

Now that some SDSS results are in the public domain, perhaps a similar piece of research could be done using those? The good news is that SDSS uses a completely different method to select objects for specta than 2dF did, so if similar analyses of the two datasets yield similar results there'll surely be no place to hide!

I particularly liked the approach taken here: a proponent in one camp suggests a method of analysis, and a neutral third party carried out the work, using publicly available data. What's good? The method and expected outcomes were clearly defined BEFORE the work was done, and the datasets are in the public domain (you don't like the conclusions? there's nothing at all stopping you from performing your own analyses!)

Yes, thank you for the link Chronos! Nereid summed up my feelings pretty well. As we discussed earlier (in this thread, I think) I feel that there is solid observational evidence for intrinsic excess redshift, but I am philosophically (intuitively, more likely) repelled by the thought that redshift might be quantized. I am prepared to accept a mechanism for excess redshift that can produce a smooth continuum of values, but quantization of redshift values in objects as apparently violent and energetic as quasars just goes against my grain. Please note the very precise reasoning (including all relevant maths) for my position. :smile:
 
  • #77
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Arp and his ideas have been one of my favorite readings, but I've kinda lost contact since some of the observations of the last few years.

Good to see he's still out there "giving 'em hell"!
 
  • #78
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turbo-1 said:
Sure! I found it pretty easily and I had foolishly assumed that everyone interested in this thread had reviewed it. The "fingers of God" distribution of galaxies in the Virgo cluster, the K-effect (intrinsic redshifts of supermassive young stars in our own galaxy, SMC, and LMC), and other arguments for intrinsic redshift are presented in the paper, but the real giant-killer is the very simple straightforward examination of already-existing redshift measurements in the M31 cluster and the M81 cluster.

http://adsabs.harvard.edu/cgi-bin/n...J...430...74A&db_key=AST&high=40f19ad6db11758
Been meaning to post a reply to this for quite a while now. Thanks Chronos and turbo-1 for the links.

The Arp paper was richer than turbo-1's build up implied (to me anyway). For example, it contained a section ("Comments on Galactocentric Corrections to Heliocentric Spectral Shifts") that introduces an important consideration which makes the LG a much more difficult group to study (in terms of Arp's thesis). In fact, given how massive the Milky Way is (wrt M31), and the lack of any data (?) on transverse motions, I wonder how any conclusion about the LG could have been drawn from the data Arp had available at the time.
Arp 0, N+T 0.

So if just the M31 sub-cluster (my term, not Arp's) is examined, then there are surely too few data points in Arp's paper to make any kind of case.
turbo-1 0.

What about the M81 group? N+T's paper didn't examine this, and Arp's didn't give a table of values, just a figure (with 11 group members, other than M81). In this case, the galactocentric corrections are much less problematic, and the measured radial velocities apparently accurate enough. Interesting case.
Arp 1.

Then we have the fingers of god. I didn't read this part too carefully, partly because it's obvious that there's far, far more high quality data now than when Arp wrote in 1994.

Which brings me to an important point. Arp’s paper is now 10 years old, and reading it one has a faint sense of surprise … only 25 LG members (cf 45+ recognised today); some tough calls about LG membership (cf the ease with which stars can be resolved in target galaxies today); no mention of high velocity clouds, star streams, etc; how the determination of redshifts then were apparently a rather big undertaking (cf 2dF and SDSS, which routinely took/take hundreds in one go); …

Surely a month or two’s work, mining some of the existing, public astronomical databases could increase the amount of data relevant to Arp’s thesis by an OOM or two?
 
  • #79
turbo
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Nereid said:
So if just the M31 sub-cluster (my term, not Arp's) is examined, then there are surely too few data points in Arp's paper to make any kind of case.
turbo-1 0.
Didn't you mean turbo-1 1? I pointed out that the closer relative masses of MW and M31, etc made the local group problematic - which is WHY N-T chose it to try to refute Arp. If they had chosen the M81 group, they could not have made any logical argument against Arp's thesis, or at least they wouldn't have been able to slip their "non-substitutive ordination" trick past the referees (I hope :yuck:). I explained why N-T decided to use the local group at least a couple of times in the thread. Perhaps I wasn't clear.

Nereid said:
What about the M81 group? N+T's paper didn't examine this, and Arp's didn't give a table of values, just a figure (with 11 group members, other than M81). In this case, the galactocentric corrections are much less problematic, and the measured radial velocities apparently accurate enough. Interesting case.
Arp 1.
Yes, very interesting indeed. If all of M81's neighboring galaxies have decided to run away from Earth, we must be a scary bunch! Seriously, no reputable cosmological model permits us to occupy such a priviliged location in the Universe, not only with respect to the apparent preferential recession of M81's companions, but also with respect to the much larger "Fingers of God" artifacts that show up in our redshift data. To those not familiar with this, just Google "Fingers of God" and you will find otherwise rational people discussing the artifacts, with some really clever explanations as to how they can be explained away. (You'll laugh! You'll cry! :smile:) More "epicycles" to tack onto our cosmology to hold it together... The artifacts in the data are real, but they are not due to "streaming effects" etc, etc (which put us back in the forbidden favored-observer position), but are instead due to a deficiency in our understanding of the causes of redshift. The Cosmus site
http://astro.uchicago.edu/cosmus/projects/fog/
calls these artifacts "glitches" and has done us all a favor by removing them from their fly-through visualization of the SDSS data. How nice of them. There is something causing these apparent redshift differentials that we do not fully understand. Since understanding and accurately measuring redshift is a vital tool in cosmology, you'd think that we would pour funding into discovering the deficiency in our understanding of redshift that allows the "Fingers of God" to show up in our redshift maps. Instead, those scholars simply "retouched the images" to make those disturbing artifacts go away. So sad. That is not science, it is the negation of science in the protection of orthodox beliefs. Edwin Hubble is probably spinning in his grave. Redshift=distance has been a very handy approximation, but it is only a tool, not an immutable law of the Universe. It's time to refine the model.

We KNOW that the artifacts exist in our redshift maps (SDSS data) and we KNOW that the F.O.G. cannot be due to the actual distributions of the galaxies. Logically then, our measurements of redshift cannot be strictly interpreted to equate to distance. Case closed. What other causative factor(s) can there be for the redshift differentials? That is one of the biggest questions still hanging...and cosmology is due for a thrilling ride when enough people start asking the right questions.

When the sacred redshift=distance has to be modified (and it WILL:wink:), it will put a lot of balls in play, including the Big Bang, cosmological expansion, the nature of quasars, "missing mass", etc, etc. Now would be a great time to be starting out as a student of Physics/Astronomy/Cosmology because the field will be wide-open for bright open-minded researchers.
 
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  • #80
Nereid
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Quite a response turbo-1! Just to get back quickly on a couple of things:

- M81 group: if 20 members of the LG have been added in ~10 years (nearly doubling its membership), how many 'unseen' members of the M81 group are there? How much has our understanding of this group advanced in a decade? Some examples: is it really an isolated group (maybe there is an attractor)? what is the distribution of dwarf galaxies (perhaps these really do matter in the group, being the tip of very large DM icebergs)?

- fingers of god: I don't think that you did justice to the consensus view of these. In a few words, if cluster members are gravitationally bound, they will have to/from Earth motions (observed as redshifts) reflecting their 'orbits' in the cluster. If the cluster is relaxed, we can measure those motions, apply the virial theorem, and get an estimate of the total mass of the cluster. The more massive the cluster, the greater the dispersion of redshifts around the cluster (weighted) mean. These dispersions will show up, on 2dF or SDSS sky maps, as fingers of god. None of this is a big secret; in fact, these cluster dispersion measures of cluster mass are one of the sets of observations which imply lots of dark matter in clusters (and one which is, IIRC, inconsistent with MOND).

Arp asserted that there is a considerable excess of 'from' motion (higher redshift than the cluster mean) than 'to' motion (lower redshift), at least for the Virgo cluster. I said that Arp's assertion should be able to be tested using the huge amount of data that we now have.

In the next post, I will propose a research project, for you and me and at least one other person (of course, all PF members are welcome to join), to do a simple test of Arp's fingers of god assertion.
 
  • #81
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Nereid said:
- M81 group: if 20 members of the LG have been added in ~10 years (nearly doubling its membership), how many 'unseen' members of the M81 group are there? How much has our understanding of this group advanced in a decade? Some examples: is it really an isolated group (maybe there is an attractor)? what is the distribution of dwarf galaxies (perhaps these really do matter in the group, being the tip of very large DM icebergs)?
What kind of attractor could pull M81's companions from its grasp? There is no visible object in that direction that serves the purpose, and the gravitational force of the attractor would have to be huge. I think we can discount that one, unless it is a huge well of "dark matter" located very near the opposite side of M81 from us. (another preferred-observer situation)

Nereid said:
- fingers of god: I don't think that you did justice to the consensus view of these. In a few words, if cluster members are gravitationally bound, they will have to/from Earth motions (observed as redshifts) reflecting their 'orbits' in the cluster. If the cluster is relaxed, we can measure those motions, apply the virial theorem, and get an estimate of the total mass of the cluster. The more massive the cluster, the greater the dispersion of redshifts around the cluster (weighted) mean. These dispersions will show up, on 2dF or SDSS sky maps, as fingers of god. None of this is a big secret; in fact, these cluster dispersion measures of cluster mass are one of the sets of observations which imply lots of dark matter in clusters (and one which is, IIRC, inconsistent with MOND).
There is no big secret, here, but there the "consensus view" is full of misdirection and apologia regarding these artifacts. There is no doubt that the Fingers of God distribution of galaxies in the SDSS data exists. There is considerable differentiation, however, in the explanations regarding how the artifacts arose, and the "proper" methods by which they should be filtered out. I will not attempt to explain away or refute every "epicycle" that has been floated to try to massage these artifacts away. The F.O.G. are in the data and have not been adequately explained.

I suggest that the SDSS data is accurate. Nothing more. Given that the data is accurate, and given that the Earth cannot be at the center of the Universe (in the sense of a preferred reference point) we must come to the understanding that our redshift data does not accurately describe the distribution of the galaxies observed. That is a given. You say that orbital motions of galactic clusters will distort their redshifts to stretch the apparent shape of each cluster so that it appears pointed toward us. Do you see a parallel with the "shape" of the M81 group (M81 "closest to us", companions "streaming away")? This should be a cause for reflection.

Nereid said:
Arp asserted that there is a considerable excess of 'from' motion (higher redshift than the cluster mean) than 'to' motion (lower redshift), at least for the Virgo cluster. I said that Arp's assertion should be able to be tested using the huge amount of data that we now have.

In the next post, I will propose a research project, for you and me and at least one other person (of course, all PF members are welcome to join), to do a simple test of Arp's fingers of god assertion.
I have been working about 60 hours a week on a very large project that is critical to my company, and I see little respite for the near term (another 3 months or so), so I hope the proposed project is not time-intensive. I have had a few moments today to post, but worked most of the day, and expect to have to work all Sunday, as well. Bleah! :yuck: I welcome the prospect that others may join in the investigation into the source of the F.O.G. I must say up-front, however, that some *very* competent folks have been working for years to make those Earth-centered radial streaks in the SDSS data "go away", with varied degrees of success.

The artifacts are in the data, and rather than invent mechanisms to refute them, we would be better served by an open-minded effort to discover what deficiency in our understanding of redshift allows these distortions to exist.
 
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  • #82
turbo
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Nereid said:
- fingers of god: I don't think that you did justice to the consensus view of these. In a few words, if cluster members are gravitationally bound, they will have to/from Earth motions (observed as redshifts) reflecting their 'orbits' in the cluster. If the cluster is relaxed, we can measure those motions, apply the virial theorem, and get an estimate of the total mass of the cluster. The more massive the cluster, the greater the dispersion of redshifts around the cluster (weighted) mean. These dispersions will show up, on 2dF or SDSS sky maps, as fingers of god. None of this is a big secret; in fact, these cluster dispersion measures of cluster mass are one of the sets of observations which imply lots of dark matter in clusters (and one which is, IIRC, inconsistent with MOND).
OK, a couple of difficulties with the consensus view of the FoG. For the reshifts of these galaxies to be smeared radially as they are in the data, their orbital velocities need to be very large - somewhere on the order of 1000 km/s. To produce those velocities, the central galaxies would have to be VERY massive (here comes the elusive dark matter again).

Another problem: as you pointed out, we would expect the smaller glaxies to swarm around the largest galaxy in each cluster, some moving toward us and some away from us to produce the radial smearing. Why don't we see that orbital motion expressed in the M81 cluster? As you can see in the Tully catalog quoted here (the basis for Arp's calculations):
http://www.seds.org/messier/more/m081gr.html [Broken]
M81's companions are all preferentally streaming away from us. The shape of the cluster would seem to be elongated (with M81 closest to us and pointing at us), but this effect is not caused by orbital motions of the small galaxies. The orbital motions of these small galaxies must contribute to their measured redshifts, but that contribution is overwhelmed by *something* that gives them much more excess redshift and makes them appear to be all receding from us relative to M81.

Another little wrinkle: on larger scales, the Kaiser Effect would dominate, causing the clusters to look flattened, not elongated. It is suggested by conventional cosmologists that this effect only occurs on supercluster scales, but it's evident that there is a lot of "wiggle-room" in the consensus view.
 
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  • #83
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I have two questions to anyone who knows..

First: Are there known interacting systems with more or less equal mass with a redshiftdifference like this (M51)

Second: Are there known interacting systems like M51 consisting of a bigger and a smaller system with no redshift difference?

thanks in advanve

Rob :)
 
  • #84
turbo
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rob_we said:
Are there known interacting systems like M51 consisting of a bigger and a smaller system with no redshift difference?
Rob :)
If I can be permitted to modify your question just a bit, "are there known interacting systems like M51 in which the smaller companion has LESS redshift than the dominant galaxy?" This should happen about 50% of the time, if redshifts are caused only by cosmological distance (due to expansion) and by the proper motion of the associated galaxies.

ADDED: Actually, the smaller companion should have more redshift less than 50% of the time. There will be times when the proper motion of the small galaxy is perpendicular to our line of sight, and therefore should exhibit no redshift differential. The instances when the redshift of the smaller galaxy is less than or equal to the host should therefore outnumber the instances when the smaller galaxy has the greater redshift. END OF ADDITION

If the small companions are more redshifted than their hosts a statistically significant percentage of the time, then there must be something we don't yet understand that is producing the excess redshift.
 
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  • #85
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Welcome to Physics Forums rob_we!

Your last post was quite interesting, but did you know that we have an entire section devoted to the exploration of theories such as yours? It's called Theory Development.

Perhaps Phobos or Janus could move rob_we's post there, as the start of a new thread (with a link back to this thread)?
 
  • #86
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rob_we's post has been moved to Theory Development.
 
  • #87
turbo
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Nereid said:
Now that some SDSS results are in the public domain, perhaps a similar piece of research could be done using those? The good news is that SDSS uses a completely different method to select objects for specta than 2dF did, so if similar analyses of the two datasets yield similar results there'll surely be no place to hide!
Hi Nereid! I thought you might want to see this. I have been quite uncomfortable with the concept of "quantization" of quasar reshifts, but the quasars pulled out of the SDSS data do seem to cluster. Any comments?

http://citebase.eprints.org/cgi-bin/citations?id=oai%3AarXiv%2Eorg%3Aastro%2Dph%2F0409025 [Broken]
 
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  • #88
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turbo-1 said:
Hi Nereid! I thought you might want to see this. I have been quite uncomfortable with the concept of "quantization" of quasar reshifts, but the quasars pulled out of the SDSS data do seem to cluster. Any comments?

http://citebase.eprints.org/cgi-bin/citations?id=oai%3AarXiv%2Eorg%3Aastro%2Dph%2F0409025 [Broken]
I would be reluctant to cite that paper as authoritative. He makes a number of assertions that are, at best poorly explained; e.g.;

1] "If high-redshift quasars are ejected from the nuclei of low-redshift galaxies, as some have claimed, a large potion of their redshift must be intrinsic [non-Doppler]."
a) What about high-redshift quasars that cannot be associated with low-redshift galaxies [which are intrinically much brighter than their ejected offspring, according to this paper]
b) Non-Doppler? It has generally been assumed that redshifts exceeding z=1 are exclusively non-Doppler. What mechanism explains Z>2 intrinsic redshifts? Gravity?

2]"Since the term local model can be misleading, by implying that all quasars are local, the term decreasing intrinsic redshift model (DIR model) will hereafter will be used"
a) While the term 'DIR model' is indeed used thereafter, a description of the 'model' is conspicuosly absent, aside from claiming it mostly makes the same predictions as the standard model.

Upon checking, I concluded Bell has a history of writing almost exclusively in support of intrinsic/quantized red shift and QSO ejection models, and makes generous use of speculative assumptions.
 
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  • #89
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Chronos said:
I would be reluctant to cite that paper as authoritative. He makes a number of assertions that are, at best poorly explained; e.g.;
Ignore his assertions for now. Just look at Figure 1 for a while. The clustering of the SDSS quasar redshifts should raise questions. Is there any mechanism you can think of that would cause the clustering at these redshift values? In past studies, such clustering has been attributed to faulty selection criteria, sensitivity/binning artifacts, etc.

Chronos said:
1] "If high-redshift quasars are ejected from the nuclei of low-redshift galaxies, as some have claimed, a large potion of their redshift must be intrinsic [non-Doppler]."
a) What about high-redshift quasars that cannot be associated with low-redshift galaxies [which are intrinically much brighter than their ejected offspring, according to this paper]
b) Non-Doppler? It has generally been assumed that redshifts exceeding z=1 are exclusively non-Doppler. What mechanism explains Z>2 intrinsic redshifts? Gravity?
He made the point quite clearly that "Hubble flow" and "Doppler" effects, caused by cosmological expansion and proper motion, respectively, cannot explain the clumping of the quasar's redshifts around certain values. Not everybody assumes that redshifts exceeding z=1 are "exclusively non-Doppler".

Chronos said:
2]"Since the term local model can be misleading, by implying that all quasars are local, the term decreasing intrinsic redshift model (DIR model) will hereafter will be used"
a) While the term 'DIR model' is indeed used thereafter, a description of the 'model' is conspicuosly absent, aside from claiming it mostly makes the same predictions as the standard model.
He is citing an evolutionary model for quasar production proposed by Arp, Burbidge, et al. Quasars are ejection phenomena. They start out at high redshift and evolve to lower-redshifts. This is a model of quasar evolution only, not an over-arching cosmological model.

Chronos said:
Upon checking, I concluded Bell has a history of writing almost exclusively in support of intrinsic/quantized red shift and QSO ejection models, and makes generous use of speculative assumptions.
You will find that Arp and Burbidge (and others) write about intrinsic redshifts and quasar ejection. That does not make them wrong. Their model makes a lot more sense than the standard model, which places quasars very far away based on their redshifts.

Believers in the standard model think the redshift of quasars is due to cosmological expansion, which places them at huge distances. This causes quasars to have properties that are a lot more troubling than intrinsic redshift, including:
1) More energy output than a hundred galaxies
2) Very highly organized and powerful even in the infancy of the universe (a problem for the heirarchical model)
3) Short-term output fluctuations that limit their size (smaller than the diameter of our solar system)
4) Some ejection jets that exhibit apparent superluminal motion
All of these problems go away if quasars are relatively nearby objects with intrinsic redshift. Is the Hubble redshift/distance relationship so sacred that we must accept monsters with these problems to prevent its violation?

Questions: If a black hole is slingshotted out of the center of a galaxy and starts gobbling matter, what would it look like? Would it look very energetic? If its accretion disk was initially very small and close to its event horizon, would the light from that disk be very redshifted? Would the redshift of the light from that disk gradually decrease as the disk gets larger and extends farther from the intense gravity well of the black hole? These questions lead to a very over-simplified model of quasar evolution that is nevertheless a lot more palatable than the standard model (see problems 1-4 above).

I am still not comfortable with quantization or preferred redshift values, but Figure 1 is pretty compelling. If the redshifts of quasars are entirely due to cosmological expansion, we should see a smooth distribution of quasar redshifts, but here is the SDSS sample of over 5000 quasars, and their redshifts are clumped in a regular fashion. Is there any way to explain this clumping without invoking intrinsic redshifts? If so, I would like to hear about it. :rolleyes:
 

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