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#11
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Barred galaxies mass distribution
Oh No wrote:
As far as galaxy evolution models are concerned, we know that CDM models don't work at all well in creating observed galaxy profiles, and we know that we have a problem understanding the rate of galaxy formation from the big bang. Unless you have a mouse in your pocket, that is your unsupported opinion; as the Scientific American article I've now URLed here twice explains, one of the reasons for the broad acceptance of CDM is exactly its explanatory power concerning the development of galaxies. Please _do_ stop presenting your opinion here as "fact" in support of your teleconnection theory, where that opinion is at odds with pretty much all cosmologists. xanthian. [Mod. note: it is of course possible for a model to be good at explaining how galaxies form and yet have some problems in reproducing the details. The issue is whether the successes make you want to solve the problems by tweaking the model, or whether you should tear it up and start again -- mjh] |
#12
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Barred galaxies mass distribution
Thus spake Kent Paul Dolan
Oh No wrote: As far as galaxy evolution models are concerned, we know that CDM models don't work at all well in creating observed galaxy profiles, and we know that we have a problem understanding the rate of galaxy formation from the big bang. Unless you have a mouse in your pocket, that is your unsupported opinion; Please do not make unsupported ad hominem attacks on my scientific integrity. I would not say such a thing as unsupported opinion. According to evolutionary models dark matter halos should have steep central density cusps (e.g., Navarro, Frenk, & White 1997) but they appear not to (e.g., de Blok, Bosma, & McGaugh 2003; Swaters et al. 2003). In a survey of about 3000 galaxies, Biviano & Salucci (2006) find that X-ray determination of the baryonic component of dark matter haloes fits evolutionary models, but subhalo components do not. Martel and Shapiro (2003) have examined the profile of lenses for a number of evolutionary models. While they find quantitative fits for many properties, they find that the models do not correctly reproduce the central region. Park and Ferguson (2003) studied the lensing produced by Burkert haloes and found, `For the scaling relation that provides the best fits to spiral-galaxy rotation curve data, Burkert halos will not produce strong lensing, even if this scaling relation extends up to masses of galaxy clusters. Tests of a simple model of an exponential stellar disk superimposed on a Burkert-profile halo demonstrate that strong lensing is unlikely without an additional concentration of mass in the galaxy center (e.g. a bulge)'. In a one study for which a particularly good analysis is possible, Wayth et al. (2005) found that, for the optical Einstein ring gravitational lens ER 0047-2808, lensing is consistent with a halo of the same mass distribution as the galaxy itself. This result is not consistent with either the halo distribution required to produce galactic rotation curves, or with evolutionary halo models. It is, of course, trivially consistent with both in a no CDM model. Incidentally straight MOND does not resolve these problems, because it finds it difficult to account for the strength of lensing. MONDian galaxies are short on mass. The teleconnection survives because it predicts greater lensing angles from distant galaxies. MOND also has a problem with galaxy clusters and Lyalpha absorbers. These are modelled from hydrodynamic principles, not from rotation curves. Again the teleconnection does not have that problem because it modifies the interpretation of Doppler shift, not Newtonian dynamics. Biviano A. & Salucci P., The radial profiles of the different mass components in galaxy clusters accepted in A&A. astro-ph/0511309. de Blok, W.J.G., Bosma, A., & McGaugh, S.S. 2003, MNRAS, 340, 657. Martel. H. and Shapiro P. R., 2003, Printed 4 March 2006, MNRAS, astro- ph/0305174 Navarro, J. F., Frenk, C. S., & White, S. D. M. 1997, ApJ, 490, 493. Park Y., Ferguson H. C., 2003, Ap.J. 589, L65-L68, astro- ph/0304317 Power C., Navarro. J. F., Jenkins A., Frenk C. S., White S. D. M., Swaters, R.A., Madore, B.F., van den Bosch, F.C., & Balcells, M. 2003, ApJ, 583, 732 Wayth R. B., Warren S. J., Lewis G. F., Hewett P. C., 2005, MNRAS, 360, 1333-1344. as the Scientific American article I've now URLed here twice explains, one of the reasons for the broad acceptance of CDM is exactly its explanatory power concerning the development of galaxies. I have cited some of the literature. There is a lot more if you would look for it. Now will you accept your own criterion that since observations on CDM are inconsistent the theory should be scrapped? [Mod. note: it is of course possible for a model to be good at explaining how galaxies form and yet have some problems in reproducing the details. The issue is whether the successes make you want to solve the problems by tweaking the model, or whether you should tear it up and start again -- mjh] Indeed. Only rarely is theory scrapped wholesale and starts again from scratch just because of inconsistent observations, especially when observations are hard to come by, to interpret and to analyse. At a theoretical level the teleconnection is a very small tweak to general relativity. It does not modify classical gtr at all, but applies in the quantum domain. The one change is that light from distant stellar objects is then treated quantum mechanically. This does mean we have to reinterpret almost all astronometrical data. The result of doing so is that no other alterations to known physics appear to be required on empirical grounds - no CDM, no Lambda, possibly no missing matter, and certainly no modification to Newtonian Dynamics. Regards -- Charles Francis substitute charles for NotI to email |
#13
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Barred galaxies mass distribution
On Feb 16, 2:19 am, "Kent Paul Dolan" wrote:
"Ken S. Tucker" wrote: though I think the Newtonian Roche Limit induction is adequate. ??? Why would there be a Roche Limit involved? If I understand correctly, that's the point at which solid bodies orbiting larger bodies are torn to pieces by tidal forces. But at the scales involved, galaxies aren't solid bodies at all, they are swarms of particles. The galaxy may well be torn apart by tides, but surely the math is different than "Roche Limit" math? For a basic ref... http://en.wikipedia.org/wiki/Roche_limit Generally the object undergoing tidal deformation, such as a galaxy, could be regarded as a gravitationally bound set of particles of zero pressure, for purposes of computation. Interestingly, the tides on Earth deform it into a prolate spheroid with "high" tide on two sides of the Earth. It appears to me (subjectively) barred galaxies often have two main arms, and when rotation is accounted for suggests a Roche limit / tidal deformation. Has a simulation of that been done that anyone might provide as a ref? Thanks Ken |
#14
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Barred galaxies mass distribution
On Feb 17, 4:23 am, "Ken S. Tucker" wrote:
On Feb 16, 2:19 am, "Kent Paul Dolan" wrote Why would there be a Roche Limit involved? If I understand correctly, that's the point at which solid bodies orbiting larger bodies are torn to pieces by tidal forces. But at the scales involved, galaxies aren't solid bodies at all, they are swarms of particles. The galaxy may well be torn apart by tides, but surely the math is different than "Roche Limit" math? For a basic ref...http://en.wikipedia.org/wiki/Roche_limit Sorry, then I certainly did NOT understand correctly, since I had it exactly backwards, a body solid enough to have tensile strength is the one that doesn't exactly obey a Roche limit calculation. Thanks for the help. xanthian. |
#15
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Barred galaxies mass distribution
On Feb 16, 3:22 pm, "Kent Paul Dolan" wrote:
Oh No wrote: As far as galaxy evolution models are concerned, we know that CDM models don't work at all well in creating observed galaxy profiles, and we know that we have a problem understanding the rate of galaxy formation from the big bang. Unless you have a mouse in your pocket, that is your unsupported opinion; as the Scientific American article I've now URLed here twice explains, one of the reasons for the broad acceptance of CDM is exactly its explanatory power concerning the development of galaxies. And what sort of explanatory power does CDM have except saying that whatever matter short fall is due to CDM. Is there a CDM theory that explains both the large elliptical galaxies and the LSB galaxies? I am sure with the amount of the broad acceptance there should be one paper that explains both with a single theory. Please do point me to such a paper. Also it should use only one psuedo free parameter per galaxy (the M/L ratio). It could have multiple universal parameters. That is what MOND/TeVeS can achieve. I don't care that it doesn't work well at Cluster level (maybe there is some kind of dark matter between galaxies). But MOND/TeVeS proves that it is possible to predict galactic rotation curves without any other free galactic parameter except M/L ratio. Till any CDM theory can do that, it is suspect at the Galactic level. xanthian. [Mod. note: it is of course possible for a model to be good at explaining how galaxies form and yet have some problems in reproducing the details. The issue is whether the successes make you want to solve the problems by tweaking the model, or whether you should tear it up and start again -- mjh] |
#16
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Barred galaxies mass distribution
wrote:
Also it should use only one psuedo free parameter per galaxy (the M/L ratio). Unfortunately for your contention, and as the Hubble dark matter map shows, CDM may exist in galaxies, but it is not limited to galaxies, and so "one pseudo-free parameter" as a goal is an uncatchable ephemera. Instead, CDM will have an inherent local intergalactic density of its own, which should influence its density within the embedded galaxies, adding a second parameter. Also as shown by the Hubble map, the intergalactic density of CDM evolves with time, adding yet a third parameter. Beyond all that, I'm a math major, not an astronomer, and if you insist in writing in acronyms, I will have to insist on not having a clear understanding of what you try to convey. Lastly, do your own homework. Google Scholar will work just as well or ill for you as for me, and you have the specialist vocabulary to put it to easier use. FWIW xanthian. |
#17
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Barred galaxies mass distribution
On Feb 19, 9:47 pm, "Kent Paul Dolan" wrote:
wrote: Also it should use only one psuedo free parameter per galaxy (the M/L ratio). Unfortunately for your contention, and as the Hubble dark matter map shows, CDM may exist in galaxies, but it is not limited to galaxies, and so "one pseudo-free parameter" as a goal is an uncatchable ephemera. I don't understand how the dark matter map makes any difference because it is generated using standard Relativity. If we assume that Relativity does not work well at very low acceleration, then the map will be wrong. So it actually doesn't prove anything. Its actually a case of circular reasoning. Instead, CDM will have an inherent local intergalactic density of its own, which should influence its density within the embedded galaxies, adding a second parameter. Let me first define the only two terms that I used MOND is MOdified Newtonian Dynamics, it says that the laws of gravitational force is different than what is predicted by Newtonian gravity when accelaration due to gravity is too low. It embodies a single equation which gives the new equation for the force law that will apply when the accelaration due to gravity is too low. It is not a proper theory and cannot be used for other things that Relativity predicts like Gravitational Lensing. MOND is ad-hoc and was designed to obtain the Tully Fisher Relationship. TeVeS is a theory based on MOND's hypothesis. It is proper theory in that it can be used for Gravitational Lensing. It basically reduces to Newtonian regime at higher accelaration due to gravity, to Relativity at higher speed, and to MOND at lower accelaration due to gravity and low speed. MOND has been quite successful in fitting rotational speed data for the galaxies. It has been tested on over 120 galaxies and there have been no failures. Please see http://www.astro.umd.edu/~ssm/mond/. If it had no truth behind it there would have been some failures in the nearly 30 years that it has existed, but there has been none. It does not work as well in the Clusters of galaxies, so I guess that there may be some kind of Dark Matter there. But at least according to MOND there is no evidence of dark matter in the galaxies. It could be that there is some kind of dark matter that can form stable structures at much larger scales than galaxies. And these structures are present in most clusters. It could be that MOND is still an approximation of some other theory that we don't know. I would like to believe that it is some kind of Conformal Field Theory, just like the other forces. BTW MOND can obtain the data from Clusters of Galaxies if 2eV massive nutrinos could form huge stable structures and was present in most galaxy clusters. Also as shown by the Hubble map, the intergalactic density of CDM evolves with time, adding yet a third parameter. Beyond all that, I'm a math major, not an astronomer, and if you insist in writing in acronyms, I will have to insist on not having a clear understanding of what you try to convey. Well I am Computer Programmer and not a scientist, and also very interested in the game we call nethack ;-). Just got interested in the MOND thing a couple of years back and have been reading everything that I can find on the subject. I find the results quite intriguing. Lastly, do your own homework. Google Scholar will work just as well or ill for you as for me, and you have the specialist vocabulary to put it to easier use. Unfortunately I don't know much about maths. And these Relativity papers are all filled up with so much maths that it makes the head hurt, and they don't go about explaining the consequences of their equations. I did find Conformal Theory from Mannheim interesting because he did bring his equations to lay man perspective. Hope I am not too full of it. FWIW xanthian. |
#18
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Barred galaxies mass distribution
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#19
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Barred galaxies mass distribution
On Feb 20, 4:19 am, wrote:
http://www.astro.umd.edu/~ssm/mond/ I went through the FAQ at that site. MOND seems to be self-falsifying. It wants us to believe that there is a very low acceleration law of gravity, and a normal acceleration law of gravity, and that the atoms in a star, which of necessity are in the "high acceleration" regime _because_ they are in a star, are *at the very same time* in a "low acceleration" regime due to gravity of distant stars accumulated as a "center of galaxy" force. That's just too much handwaving to swallow. MOND may well _fit_ mass/light for galaxies, but making equations to fit is presumably "easy" for those comfortable with that level of math. What MOND does not do is _explain_ the rotation of galaxies, and its attempts to do so are just silly, as far as I can tell. In comparision, CDM attempts to _explain_ galaxy rotations, and evidence that CDM (and Cold Dark Energy) exist seems to accumulate regularly, the Hubble survey being merely one prominent example. FWIW xanthian. Notice also that checking whether accelerations at the MOND level exist is perfectly straightforward (if tedious) to do in an earth based lab. If you can factor away the gravity inside a star as MOND proponents pretend is possible, you can surely factor away the lesser gravity of earth to detect with interferometry whether two appropriately sized and spaced masses attract each other "differently in essence" above and below the a0 parameter gravitational behavior regime breakpoint of MOND. If thirty years after MOND was proposed that still hasn't been attempted and the results documented, why is MOND still being taken seriously? An appropriate place to attempt that Real Soon Now. would be the "under improvement" earth based gravity wave detection facilities where effects of outside vibration will be carefully controlled and culled from the data, and detection of such minor motions are a design goal. http://news.bbc.co.uk/1/hi/sci/tech/2774163.stm |
#20
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Barred galaxies mass distribution
Thus spake Kent Paul Dolan
On Feb 20, 4:19 am, wrote: http://www.astro.umd.edu/~ssm/mond/ I went through the FAQ at that site. MOND seems to be self-falsifying. An empirical law found purely from observation cannot be self falsifying. It wants us to believe that there is a very low acceleration law of gravity, and a normal acceleration law of gravity, and that the atoms in a star, which of necessity are in the "high acceleration" regime _because_ they are in a star, are *at the very same time* in a "low acceleration" regime due to gravity of distant stars accumulated as a "center of galaxy" force. That's just too much handwaving to swallow. It doesn't come with an explanation. But the observation of the fits cannot be denied. Nor can it be explained with CDM. MOND may well _fit_ mass/light for galaxies, but making equations to fit is presumably "easy" for those comfortable with that level of math. The level of maths is not that high. Laws close to MOND might also work. What MOND does not do is _explain_ the rotation of galaxies, and its attempts to do so are just silly, as far as I can tell. Actually attempts like Bekenstein's TeVes and Moffat's scalar tensor theory are quite sophisticated. In comparision, CDM attempts to _explain_ galaxy rotations, and evidence that CDM (and Cold Dark Energy) exist seems to accumulate regularly, the Hubble survey being merely one prominent example. Not really. Lensing profiles and evolutionary models appear to falsify it quite well, as does the baryon catastrophy. The Hubble survey is not evidence if it assumes an incorrect lensing law. Notice also that checking whether accelerations at the MOND level exist is perfectly straightforward (if tedious) to do in an earth based lab. It's well established that MOND does not apply in the inner solar system. Nor does the Pioneer blueshift. If thirty years after MOND was proposed that still hasn't been attempted and the results documented, why is MOND still being taken seriously? Because many cosmologists don't find CDM a credible explanation, and the fits to the MOND law are definite empirical evidence which is also mounting. It also applies to globular clusters, in which CDM is a non- starter as an explanation - it would mean inconsistent amounts of CDM in the cluster as is supposed to exist within the Milky Way. The teleconnection does explain these observations, by modifying redshifts and lensing, and without modifying either particle physics or dynamics. Regards -- Charles Francis substitute charles for NotI to email |
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