# Thread: More from Arp et al.

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Originally Posted by matt.o
This is a weak word argument which you would need to be shown to be true through some sort of rigorous mathematical/theoretical argument based on intrinsic redshifts.
Yes, eventually things like that should be analysed mathematically, but this is just a discussion, and sometimes "weak word arguments" are made during discussions.

Originally Posted by matt.o
In fact, the physical radius would be larger than the one measured using standard cosmology
No. Physical radius would be smaller, because the cluster would be closer to us than we think. Think about the Sun and the Moon. They have roughly the same angular diameter from our point of view. Moon is closer to us, and it has smaller physical diameter.

Originally Posted by matt.o
- which in fact makes no difference to the measured velocity using only the temperature and pressure differences in the shock front. Measuring the Mach number (the ratio of the velocity to the sound speed in the gas) involves measuring the ratio of the temperatures inside the shock front to that outside the shock front downstream from the gas flow. This involves fitting the Bremstrahlung x-ray spectrum along with the emission lines to a temperature, abundance and gas density. The redshift comes into it, yes, but the ratio of the temperatures are used to measure the Mach number, hence any differencedue to redshift etc will be cancelled in taking to the ratio. Not sure how the radius would make a difference-
Ahh yes, I was wrong about that. I should be more careful when dealing with things I don't know much about. Thanks for the correction.

Originally Posted by matt.o
perhaps you should read up on this stuff before proposing paradigm shifts???
Reading is always a good idea, but to me participation in these discussions is part of my "reading". However, I didn't propose any paradigm shifts, I merely hypothesized on the situation.

Originally Posted by matt.o
You must be implying intrinsic blueshifts - how else would the observed velocity dispersions show non-skewed gaussian velocity distributions?
Well, if we measure the redshifts of the members of the cluster, then take a mean of those redshifts, and then plot the distribution with reference to that mean, I'm not especially surprised of the gaussian distribution. After all, peculiar velocities are still there even if there would be intrinsic redshifts too. From the point of view of Arp's model, we perhaps** should first determine the dominant member of the cluster, the one (unless there are several of them) that could be considered to be the "parent" of other objects. Then we should plot the redshift distribution with reference to that parent galaxy's redshift and see what we have then.

It still remains to be seen if the actual distributions are gaussian. I have to do that literature review some day.

Originally Posted by matt.o
Your original question asked whether the intrinsic plus the peculiar velocity could explain anomalous peculiar velocities - how then does this explain anolmolous blueshifted (WRT the mean redshift) peculiar velocities?
If there really is large anomalous blueshifts, then with quick thinking I can't come up with any good explanation for them from Arp's model point of view. In that case it probably should be argued that such objects are just chance projected foreground objects. But those anomalous blueshifts should really be so large (larger than expected from peculiar velocities) that also mainstream would have trouble explaining them.

Originally Posted by matt.o
Well, you must be able to explain these things that mainstream astronomy has explained through gravitational interaction if you are to propose some intrinsic redshift mechanism or some mechanism through expulsion from the central galaxy, no?
Of course. I'm just not going to propose any mechanisms, I'm still in the process of determining from the observations if intrinsic redshifts are real phenomenon.

Originally Posted by matt.o
Chandra data is available to the public - how about trying to measure the temperature with the redshift left to vary?
That might be interesting, if I would have the time. I also would have to learn how to do that first. I wasn't thinking thge variance in redshift as much as variance in size of the cluster. If size of the cluster is different than we think, then initially it feels to me that it might affect our estimated temperature. But I don't know, perhaps there's a way to determine temperatures without using size of the cluster / distance to the cluster / cosmological redshift of the cluster.

Originally Posted by matt.o
The x-ray data show emission lines due to iron k-alpha emission at about 6.4keV, maybe the gas shows intrinsic redshift too?
Maybe.

** I said we perhaps have to do this, because in Arp's model there also is a possibility that the whole cluster is same aged, and in that situation there wouldn't be expected to be intrinsic redshifts in the members with reference to each other.

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Small number statistics bother me greatly - upon which my original objections to Russell's conclusions were raised. When pressed for details, Russell inserted additional selection criteria to justify his sample set. I contend that affirms my objections are well founded.

3. Originally Posted by Ari Jokimaki
Yes, eventually things like that should be analysed mathematically, but this is just a discussion, and sometimes "weak word arguments" are made during discussions.
Fair enough.
Originally Posted by Ari Jokimaki
No. Physical radius would be smaller, because the cluster would be closer to us than we think. Think about the Sun and the Moon. They have roughly the same angular diameter from our point of view. Moon is closer to us, and it has smaller physical diameter.
Of course, not quite sure what I was thinking there!
Originally Posted by Ari Jokimaki
Reading is always a good idea, but to me participation in these discussions is part of my "reading". However, I didn't propose any paradigm shifts, I merely hypothesized on the situation.
Fair enough. However, I do feel that postulating intrinsic redshifts is tantamount to proposing paradigm shifts.

Originally Posted by Ari Jokimaki
Well, if we measure the redshifts of the members of the cluster, then take a mean of those redshifts, and then plot the distribution with reference to that mean, I'm not especially surprised of the gaussian distribution. After all, peculiar velocities are still there even if there would be intrinsic redshifts too. From the point of view of Arp's model, we perhaps** should first determine the dominant member of the cluster, the one (unless there are several of them) that could be considered to be the "parent" of other objects. Then we should plot the redshift distribution with reference to that parent galaxy's redshift and see what we have then.

It still remains to be seen if the actual distributions are gaussian. I have to do that literature review some day.
Generally the cD galaxy does lie at zero peculiar velocity WRT to the mean of the cluster (in dynamically relaxed systems). The point is, an intrinsic redshift component in all galaxies in the cluster would cause a skewed velocity distribution. This is not observed.

Originally Posted by Ari Jokimaki
Of course. I'm just not going to propose any mechanisms, I'm still in the process of determining from the observations if intrinsic redshifts are real phenomenon.
And I think there is a lot more work to be done here.
Originally Posted by Ari Jokimaki
That might be interesting, if I would have the time. I also would have to learn how to do that first. I wasn't thinking thge variance in redshift as much as variance in size of the cluster. If size of the cluster is different than we think, then initially it feels to me that it might affect our estimated temperature. But I don't know, perhaps there's a way to determine temperatures without using size of the cluster / distance to the cluster / cosmological redshift of the cluster.
It would affect the measured density. I would have to look at how the temperature fits vary with redshift to say any more about this.

Matt.

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Originally Posted by Cougar
Are you kidding? Russell is doing his best to show his guru Arp is correct. Perhaps you should look through Russell's paper again, as well.
Correct, but you said young evolved into old, which is quite different than young showing characteristics different than old.

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Originally Posted by matt.o
As I said, I have followed this discussion for some time, so I know what is going on. Perhaps you can tell me if Russell's results have been confirmed using the k-band TFR, which is less sensitive to the effects of star formation? I seem toremember Russell talking about it, but i'm not sure if it has been done.
I believe he has but don't know for sure.

Perhaps you have forgotten my link to the paper way back in post #2807 regarding Virgo? They have done what you and astro_uk were discussing a while back - ie. measure the 3D distribution of galaxies using the surface brightness fluctuation method. They find groups on the front and backside of the main cluster, maybe you could check to see if the spirals in russell's samples coincide with these groups.
This is a good point. I have given the paper a cursory read now, and will give what you suggest a try in the next few days. Some preliminary comments on this. The distance data we will be comparing will be based on the calculation method of the paper for the ellipticals and either Cepheid data or TD-TFR calculations for the spirals. We will have to assume that all of these are very accurate and compatible to get the analysis this fine. What I mean by fine is, we will have to be able to determine which side of the subgroup a galaxy lies, to make a judgement on whether it should be moving toward us or away from us, for example. It's worth a go though.
TomT

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Originally Posted by matt.o
It would affect the measured density.
Umm, I think density is not affected. If the cluster is scaled smaller, the space between the objects gets smaller, but the objects themselves also get smaller by same amount, so density should stay the same.

Here's 1D illustration of the situation (m = unit of mass, . = certain distance of empty space, m also covers the same distance as "."):

Code:
```Large cluster:

..mm..mm..mm..mm

=> "1D density" = 8 units of mass / 16 distances of space
= 0.5 "1D density" units

Small cluster (1/2 the size):

.m.m.m.m

=> "1D density" = 4 units of mass / 8 distances of space
= 0.5 "1D density" units```

7. Originally Posted by Ari Jokimaki
Umm, I think density is not affected. If the cluster is scaled smaller, the space between the objects gets smaller, but the objects themselves also get smaller by same amount, so density should stay the same.
No, I was talking about gas density (since you mentioned temperature and we were discussing Chandra x-ray data). To get the gas density, you need to integrate the emission measure along the line of sight. You would probably assume spherical symmetry, hence assume the projected diameter of a circular area is the same as the line of sight diameter of the object. A difference in redshift, as you know, would cause the projected diameter to be incorrect and hence the assumed line of sight diameter would also be in error. The luminosity distance also comes into the observed x-ray flux into an emission measure.

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Originally Posted by matt.o
No, I was talking about gas density...
This didn't occur to me. Yes, I agree that gas density would be different if clusters were closer than we think. I think it means that temperature should be different. Hmm... I wonder if there's a potential distance indicator here, perhaps the gas density or temperature. Well, perhaps not, there probably is no way to tell what the density or temperature should be in different clusters.

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Originally Posted by matt.o
Generally the cD galaxy does lie at zero peculiar velocity WRT to the mean of the cluster (in dynamically relaxed systems). The point is, an intrinsic redshift component in all galaxies in the cluster would cause a skewed velocity distribution. This is not observed.
Matt, the intrinsic redshift wouldn't be in "ALL" galaxies as this is a morphology issue and as such is intimately tied to star formation rates.

IS a 'dynamically relaxed system' considered an early or late system?

Actually, how does a system become dynamically relaxed?

10. Originally Posted by Ari Jokimaki
This didn't occur to me. Yes, I agree that gas density would be different if clusters were closer than we think. I think it means that temperature should be different. Hmm... I wonder if there's a potential distance indicator here, perhaps the gas density or temperature. Well, perhaps not, there probably is no way to tell what the density or temperature should be in different clusters.
You should look up the sunyaev-zeldovich effect. It can be used to measure the gas density and along with x-ray measurements, can provide distance measurements.

Originally Posted by RussT
Matt, the intrinsic redshift wouldn't be in "ALL" galaxies as this is a morphology issue and as such is intimately tied to star formation rates.
You have taken my comment out of context - go back and read the whole conversation. I was replying to Ari's comment regarding velocity distributions not regarding the Russell paper.
Originally Posted by RussT
IS a 'dynamically relaxed system' considered an early or late system?
I am talking about galaxy clusters, which are not generally referred to as late or early type.
Originally Posted by RussT
Actually, how does a system become dynamically relaxed?
The same way most things come to equilibrium - nothing disturbs them for some period of time.

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Originally Posted by matt.o
Perhaps you have forgotten my link to the paper way back in post #2807 regarding Virgo? They have done what you and astro_uk were discussing a while back - ie. measure the 3D distribution of galaxies using the surface brightness fluctuation method. They find groups on the front and backside of the main cluster, maybe you could check to see if the spirals in russell's samples coincide with these groups.
Hi Matt,
I haven't checked relative position data yet, but have some further thoughts on this. I think you are proposing that galaxies are infalling toward one or other of the Virgo sub groups. My thought is that an infalling galaxy doesn't just reach the center and disappear, it keeps going past center and then decelerates. In other words it is really in an orbit about the sub cluster barycenter.
So, from this point of view, consider a galaxy starting at a point between us and a sub cluster. As it falls toward the center it moves away from us and is redshifted from our point of view. It moves past center, and continues moving away from us on the back side, but slowing down. At some point it reaches max distance from us, and heads back our way, starting to be blue shifted. As this continues, it reaches a point on our side of center,still moving toward us. Finally it reaches the near point to us and the cycle repeats.
The point is that the galaxy shows both blueshift and redshift (negative and positive peculiar velocity) on either side of the cluster center. So checking the positions of Russell's spirals wont really tell us anything, because his numbers showing positive and negative peculiar velocity could happen anywhere in Virgo.

TomT

12. Originally Posted by TomT
Hi Matt,
I haven't checked relative position data yet, but have some further thoughts on this. I think you are proposing that galaxies are infalling toward one or other of the Virgo sub groups. My thought is that an infalling galaxy doesn't just reach the center and disappear, it keeps going past center and then decelerates. In other words it is really in an orbit about the sub cluster barycenter.
Yes.
Originally Posted by TomT
So, from this point of view, consider a galaxy starting at a point between us and a sub cluster. As it falls toward the center it moves away from us and is redshifted from our point of view. It moves past center, and continues moving away from us on the back side, but slowing down. At some point it reaches max distance from us, and heads back our way, starting to be blue shifted. As this continues, it reaches a point on our side of center,still moving toward us. Finally it reaches the near point to us and the cycle repeats.
The point is that the galaxy shows both blueshift and redshift (negative and positive peculiar velocity) on either side of the cluster center. So checking the positions of Russell's spirals wont really tell us anything, because his numbers showing positive and negative peculiar velocity could happen anywhere in Virgo.

TomT
There is quite a lot of analysis on Virgo and its substructure in the literature, and I don't think a simple model like this is accurate. In fact, the Mei paper goes through a list of papers by Binggeli et al., who find at least 6 distinct entities within the Virgo cluster and you can see them in figure 1 of the Mei et al. paper. They are the Virgo cluster cantred on M87 (cluster A), a small subcluster cetred on M49 (cluster B), the M, W and W' clouds along with an extension to the south.

They also cite Gavazzi, who has measured the tully-fisher relation for 75 late types and the fundamental plane for 59 ellipticals finding that cluster B is infalling into cluster A (Virgo) at 750km/s.

I am not sure the excess peculiar velocities can be attributed to intrinsic redshifts without a thorough analysis of where each of Russell's galaxies lies WRT to these subgroups.

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Originally Posted by matt.o
I did not reference any paper. I think I know the paper you are talking about though, and this paper is attempting to answer the question as to whether the observed velocity is possible in the standard cosmological scenario. The velocity of the subcluster is measured directly from the shock front observed in the chandra images.
Matt.
Hi Matt,
I am not familiar with the technique used to determine the subcluster velocity in your Bullet Cluster example. I think you are right that the above paper analyzed the Bullet Cluster observations and conclusions from the standpoint of "is this possible in the standard cosmological scenario?". They found that it is a rare (one in 500) possibility but not impossible.
So the flip side of this is that such an occurrence has a 499/500 = .998 of not occurring in current standard cosmology, and thus a 99.8% probablilty that a non-standard cosmology is needed to explain it. I don't think such conditions should be used to support using a number as high as 4500 km/sec as a maximum for cluster peculiar velocities.
TomT

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Originally Posted by matt.o
You should look up the sunyaev-zeldovich effect. It can be used to measure the gas density and along with x-ray measurements, can provide distance measurements.
Ok I will, thanks.

At some point I'll also take a closer look at those high redshift cluster studies. It seems to me that they might be able to set some constraints on the intrinsic redshifts. But as this thread shall be closed in a few days, we won't be able to discuss that here.

At this point I want to thank all the participants of this thread.

15. Originally Posted by TomT
Hi Matt,
I am not familiar with the technique used to determine the subcluster velocity in your Bullet Cluster example. I think you are right that the above paper analyzed the Bullet Cluster observations and conclusions from the standpoint of "is this possible in the standard cosmological scenario?". They found that it is a rare (one in 500) possibility but not impossible.
So the flip side of this is that such an occurrence has a 499/500 = .998 of not occurring in current standard cosmology, and thus a 99.8% probablilty that a non-standard cosmology is needed to explain it. I don't think such conditions should be used to support using a number as high as 4500 km/sec as a maximum for cluster peculiar velocities.
TomT
Using the same line of argument, we could say that Russell has measured what you guys perceive as evidence for intrinsic redshifts in 8 of 2000 Virgo cluster members. So the chance of this not occuring is then 99.6%. Should this be used for evidence of intrinsic redshift (note, I have used your line of thinkning here)?

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Originally Posted by matt.o
Using the same line of argument, we could say that Russell has measured what you guys perceive as evidence for intrinsic redshifts in 8 of 2000 Virgo cluster members. So the chance of this not occuring is then 99.6%. Should this be used for evidence of intrinsic redshift (note, I have used your line of thinkning here)?
Ah, but you used the line of thinking incorrectly, for the umpth time, the evidence for intrinsic redshift is NOT based on a single group of 8 galaxies. And on top of that, the number of 2000 is misleading, as not all members of the cluster can be used for the analysis. Try to stick to the facts in a scientific exchange.

Cheers.

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Originally Posted by matt.o
Using the same line of argument, we could say that Russell has measured what you guys perceive as evidence for intrinsic redshifts in 8 of 2000 Virgo cluster members. So the chance of this not occuring is then 99.6%. Should this be used for evidence of intrinsic redshift (note, I have used your line of thinkning here)?
Actually he used the 76 galaxies listed in Table II. Of these 49 were the spirals he was able to find in Virgo that were usable for a TFR calculation. Each of the groupings in Table II show various degrees of offset in Vvir, but he noted the largest difference in redshift between spiral types ScI (8) and Sab/Sb with Log V>2.15 (9). He analyzed these 17 (not 8) in Table III.
Challengers to Russell keep repeating the same misinformation over and over, and proponents keep having to repeat the facts back over and over. I think this is a prime reason this thread will be toast in a couple weeks.
TomT

18. Originally Posted by TomT
this thread will be toast in a couple weeks.
It's not clear what will happen with the Arp thread. Because *this* thread has a fairly steady supply of new information AND people working real numbers on both sides, it might be a special case... or it might be that the Arp general topic will break down into much narrower discussions. In any case, I don't think discussion of Arp's model will end here.

19. Originally Posted by VanderL
Ah, but you used the line of thinking incorrectly, for the umpth time, the evidence for intrinsic redshift is NOT based on a single group of 8 galaxies. And on top of that, the number of 2000 is misleading, as not all members of the cluster can be used for the analysis. Try to stick to the facts in a scientific exchange.

Cheers.
Exactly, with flawed logic and misleading statements, you can disprove anything, right? That's the point (which you appeared to have missed).
Originally Posted by TomT
Actually he used the 76 galaxies listed in Table II. Of these 49 were the spirals he was able to find in Virgo that were usable for a TFR calculation. Each of the groupings in Table II show various degrees of offset in Vvir, but he noted the largest difference in redshift between spiral types ScI (8) and Sab/Sb with Log V>2.15 (9). He analyzed these 17 (not 8) in Table III.
Challengers to Russell keep repeating the same misinformation over and over, and proponents keep having to repeat the facts back over and over. I think this is a prime reason this thread will be toast in a couple weeks.
Umm, only a group of 8 exhibit a mean velocity of ~-800km/s? The other 9 exhibit a mean velocity of ~900km/s towards the Milky Way. Then how are there 17 galaxies exhibiting evidence for intrinsic redshift???? Anyway, see my above comment to VanderL.

How goes it with correlating the Mei et al. SBF galaxies with the Russell spirals?

Matt.

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Originally Posted by matt.o
Originally Posted by VanderL
Ah, but you used the line of thinking incorrectly, for the umpth time, the evidence for intrinsic redshift is NOT based on a single group of 8 galaxies. And on top of that, the number of 2000 is misleading, as not all members of the cluster can be used for the analysis. Try to stick to the facts in a scientific exchange.

Cheers.
Exactly, with flawed logic and misleading statements, you can disprove anything, right? That's the point (which you appeared to have missed).
I just wanted to make sure that Russell's paper is not misrepresented. If you only wanted to make a statement about the flaw in TomT's logic then just explain exactly what you mean.

Cheers.

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Originally Posted by matt.o
Umm, only a group of 8 exhibit a mean velocity of ~-800km/s? The other 9 exhibit a mean velocity of ~900km/s towards the Milky Way. Then how are there 17 galaxies exhibiting evidence for intrinsic redshift????
By your question, I am unsure if you realize that we are talking peculiar velociy here, not total velocity. I assume you realize we are talking peculiar velocity, so the situation is as follows.
The 8 Sab/Sb galaxies are located throughout the cluster at distances from us ranging from 12.6 to 28.1 Mpc. They show peculiar velocity ranging from -577 to -1133 km.sec, with the average being -868 km/sec.
The 9 ScI galaxies are located at distances ranging from 14.9 to 23.6 Mpc and have peculiar velocities ranging from -92 to +1154 km/sec with the average being +718 km/sec.
Russell did a Kolmgorov-Smirnov (K-S) test on the 2 data sets which resulted in a .001 probability that these 2 sets have the same distribution. So the question then arises, why is there an approximately 1600 km/sec offset in peculiar velocity between these 8 of one type and 9 of the other type (8+9=17), and why is one type blueshifted and the other type redshifted?
The proposed solution is that above values are not just peculiar velocities, but peculiar velocity + a non velocity component. If the non velocity component is subtracted out, the 17 remainders will be a compatible set of peculiar velocities which the K-S test will show to be members of the same distribution, just as the position data are.

Anyway, see my above comment to VanderL.
Don't have any interest in getting into these personal attack type comments.

How goes it with correlating the Mei et al. SBF galaxies with the Russell spirals?
Matt.
The position data are all in the Russell paper for anyone to compare with the SBF galaxies. Why don't you give it a go? I will look at it when time allows.
TomT

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Originally Posted by Thanatos
Small number statistics bother me greatly - upon which my original objections to Russell's conclusions were raised. When pressed for details, Russell inserted additional selection criteria to justify his sample set. I contend that affirms my objections are well founded.
I realize that this is a sore point with you, and probably always will be. Here is one piece of info that may shed some light on Russell's culling of candidate galaxies to the list he ended up with.
You submitted a list of 92 (I believe) galaxies that you thought should be considered. One of Russell's criteria was that no galaxies would be included with redshift total velocity > 3000 km/sec.
If you look at the paper Matt O. provided, the authors started out with about 100 E type galaxies. They excluded 5 of these because total velocity exceeded 3000 km/sec (see p.4). So here you have an independent verification of one of Russell's criteria.
So if you apply this to your 92 galaxies, you will find that 11 exceed 3000 km/sec. This one factor reduces your list to 81.
Russell's other criteria have been delineated many times.

TomT

23. Originally Posted by TomT
The proposed solution is that above values are not just peculiar velocities, but peculiar velocity + a non velocity component. If the non velocity component is subtracted out, the 17 remainders will be a compatible set of peculiar velocities which the K-S test will show to be members of the same distribution, just as the position data are.
However, I have heard nothing about a proposed method for subtracting out the hypothesized non-velocity component, or even a rationale for doing so....

As I understand it, late type galaxies, especially ScI's, have a much higher interstellar gas density than early types. This obviously has an effect on galactic rotation rates and thus Tully Fisher estimates. As astro-uk said, it's risky to use TF between different galaxy types. Russell made adjustments to lower this risk. Were his adjustments really adequate? Wouldn't this difference be a simpler explanation than invoking some unknown and unaddressed and unexplained phenomenon?

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## Max Galaxy Peculiar Velocity

In his investigation of various galaxy clusters, Russell has referred to 1500 km/sec as the apparent maximum accepted value for peculiar velocity by main stream astronomers. Matt O. has questioned whether this is way too low, with values as high as 4500 km/sec proposed for the max.
In my previous note to Thanatos I pointed out that in the paper referred to us by Matt, those authors excluded from consideration as members of the Virgo Cluster, any galaxies with total velocity that exceeded 3000 km/sec. We can use this criteria to calculate the effective max this places on cluster peculiar velocity.
Using the paper's estimate to the Virgo main sub cluster of about 17 Mpc, assume a Hubble constant of 72. This results in the equivalent redshift velocity due to expansion of 17*72 = 1224 km/sec. Subtracting this from the authors accepted max total of 3000 km/sec, gives 1776 as the corresponding max in peculiar velocity. This is higher than Russell's claimed 1500, but far below the 4500 proposed.
Since peculiar velocity in clusters arises from gravitational interaction between the member galaxies, I can think of no reason why this max in peculiar velocity should vary with cluster redshift, distance away from us in space, or for any other reason within standard cosmology.
TomT

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If it's any consolation, matt, I think I understand what you are saying. I'm otherwise a bit annoyed. I made provacative arguments about peculiar motions and nobody appears willing to admit their ATM notions might be flawed.

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Originally Posted by Thanatos
If it's any consolation, matt, I think I understand what you are saying. I'm otherwise a bit annoyed. I made provacative arguments about peculiar motions and nobody appears willing to admit their ATM notions might be flawed.
Could you expand a bit more on this so we know what you are referring to?
TomT

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Originally Posted by antoniseb
It's not clear what will happen with the Arp thread. Because *this* thread has a fairly steady supply of new information AND people working real numbers on both sides, it might be a special case... or it might be that the Arp general topic will break down into much narrower discussions. In any case, I don't think discussion of Arp's model will end here.
Interesting news, would you like bringing this into the thread where the new rule is discussed?

Cheers.

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Originally Posted by matt.o
How goes it with correlating the Mei et al. SBF galaxies with the Russell spirals?
Matt.
OK, I took another cursory look at the Mei et al paper, hopefully absorbing enough to make a reasonable answer to your questions. Very interesting read, and liked getting the table at the end on E galaxy data.
Their findings for 84 galaxies show 79 centered in a main group located between 15.3 and 17.7 Mpc distance from us. They note that within this distance range are also 3 groups centered around M87, M49 and M86. The remaining 5 galaxies in their study lie in what they call the W' cloud located at about 23 Mpc.
Relative to this layout, Russell's spirals are located as follows:
In the region less than 15.3 Mpc, there are 3 blueshifted spirals and 2 redshifted.
In the region between 15.3 and 17.7 there are 2 redshifted and 1 blueshifted.
In the region beyond 17.7 Mpc, there are 4 redshifted, and 5 blueshifted.
Of these spirals, 5 are also in the region of the W' Cloud. Of these, 2 are redshifted and 3 are blue shifted.
I don't see anything other than a random pattern in all this positon data, although all the blueshifted are one type spiral, and all the redshifted are another type.
I then took a look at the right ascension and declination of the 17 spirals relative to Fig. 8 in the Mei et al paper. I had thought maybe all the blueshifted might be on one side of center, and all the redshifted on the other, or at least close to it. If this were the case, you might be able to conclude that the spirals are in some kind of clockwise or counterclockwise pattern, which could explain their motion. Unfortunately for this point of view, all I could find was a shotgun pattern.
This is my first shot at looking at the situation. Feel free to comment. Better yet, take a look yourself and see what you come up with.
TomT

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Originally Posted by TomT
Could you expand a bit more on this so we know what you are referring to?
TomT
Deriving peculiar motion without invoking a redshift distance would be a good place to start.

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Originally Posted by Thanatos
Deriving peculiar motion without invoking a redshift distance would be a good place to start.
Could you explain further, hopefully with a sample calculation or a reference to one.
The only ways I know are:
(1) Obtain a valid distance to the object (Cepheid,TFR, SBF). Compute the equivalent redshift of this distance, which is the component due to expansion. Subtract this from the total. The remainder is what mainstream believes is entirely peculiar velocity.
(2) Do a proper motion study if possible.
(3) Use the method which Matt mentioned, which I would call an approximate method. For a cluster, calculate the average redshift of all the members. Subtract the redshift of an individual galaxy from the cluster average. Of course method 3 depends entirely on redshift distance.
TomT

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