Good current paper on mass / luminosity and rotation curves
in [Physics]
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From: eric gisse on 3 Jul 2010 16:35 Yousuf Khan wrote: > On 7/3/2010 6:49 AM, eric gisse wrote: >> Turbulence typically refers to self-interactions within a fluid. I'm >> pointing out the specific exception now rather than having to point out >> later and then deal with 'but you said there's no turbulence!!!!' >> response. >> >> Its' like people aren't listening when I say dark matter is modeled as a >> perfect fluid. What the hell do folks think that implies? > > Then it's not a perfect fluid if there are self-interactions. You can > say it's *close* enough to a perfect fluid at the galactic scale. At > bigger scales, it is not. Second of all, you do realize that all of > these "if...then...but if...else..." type behaviours of Dark Matter is > exactly what Dark Fluid is supposed to address. > > Yousuf Khan The gravitational self-interactions do not appear in the stress tensor that describes it. That's why it is a perfect fluid.
From: eric gisse on 3 Jul 2010 17:13 dlzc wrote: > Dear eric gisse: > > This topic is on topic in sci.astro. Leave it in the list of > newsgroups. If you have the "nuts" to post on sci.astro, don't alter > the Followup-to to remove it. Feature of the newsreader that I don't care enough to adjust. Followups get set to the newsgroup I read this in. It remarkably cuts down on the bullshit resulting from people who crosspost to 500 groups. > > On Jul 2, 2:17 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: >> dlzc wrote: >> > On Jun 30, 5:24 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: >> >>dlzcwrote: >> >> > On Jun 30, 12:04 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: >> >> >>dlzcwrote: >> >> >> >http://arxiv.org/abs/1005.3154 >> >> >> >> > Provides a lot of background into how Dark Matter >> >> >> > is arrived at (as a free parameter, whose spatial >> >> >> > distribution is far from simple, depending on the >> >> >> > M/L modelled internal to the target galaxy). >> >> >> >> You do know that's not the only evidence for dark >> >> >> matter, right? >> >> >> > Lest we go through your list of "evidence", what you >> >> > have supplied to date can be done with simply normal >> >> > matter. >> >> >> Not if you believe in electromagnetic theory. You require >> >> some very special pleads to make bulk amounts of >> >> hydrogen invisible, especially in *this* galaxy where radio >> >> isn't redshifted into oblivion. >> >> > "Heliosheath". >> >> A region whose density is measured in atoms per >> cubic meter, > > And yet is sufficient, given a choice of M/L model. Pretend the galaxy is a sphere that's 125,000 light years wide. Estimates of the dark matter bulge are comfortably nestled in the region of 2x10^12 solar masses, while in comparison the mass of what's directly observable is in the region of 10^10 solar masses. 125,000 light years is ~10^21 m. The volume for that sphere is ~2x10^63 m^3. 2x10^12 solar masses = 4x10^42 kg 1 kg of hydrogen = 1000 moles = 6x10^26 atoms so 2x10^12 solar masses ~ 10^69 atoms That many atoms of hydrogen in that 125,000 light year sphere would require an _average_ density of about 10^6 atoms/m^3 which is an order of magnitude or 6 higher than the average density of vacuum. Which is, in turn, a massive underestimate because I assumed the galaxy was a sphere. Add another factor of 15 or so if you want a number closer to reality. IT CAN NOT WORK. DO YOU SEE YET? You can DOUBLE the effective size of the galaxy and you will still be orders of magnitude off. > >> > Plenty of bulk hydrogen available, and invisible until >> > it is braked. >> >> Unless you point a radio telescope at the 21cm line, >> which neutral hydrogen radiates at. Or talk to an >> astronomer about the general irritant which interstellar >> hydrogen poses to observations at the galactic center. > > I'm refering to the ionized stuff, and you know that. Except the traversal of electromagnetic waves through a plasma leaves rather significant tell tale signs. The drift velocity of bulk anything about a galaxy will induce massive faraday rotation in electromagnetic waves, because you demand a wholly ionized plasma of a significant amount of hydrogen. That we don't see such polarization in the CMB, or evidence of Compton scattering off all those bulk electrons that are required, is rather telling. And review basic electromagnetic theory. You are essentially demanding that 10^12 solar masses worth of separated charge - where's the energy coming from to maintain that separation? Hmm, how much energy would that be? Hydrogen's binding energy is 13.6 eV, so you'll need 6x10^26 * 13.6eV = 8x10^27 eV worth of energy expended to do that. Any guesses as to where that energy is coming from, and how frequently it needed to be expended? > >> > And we also (purportedly) are in a sparsely populated >> > portion of the galaxy... >> >> >> > If you have something >> >> > other than rotation curves (which this paper says >> >> > uses M/L) >> >> >> What the paper actually says is the following: >> >> >> We assume that the rotation curve V(R) of the disk >> >> galaxy, for which we want to construct a >> >> mass model, is known (i.e., it has been >> >> ?observed?); as a mathematical boundary >> >> condition, we assume that the rotation >> >> curve remains flat at V_\infty out to infinite >> >> radii. >> >> > They say a lot more than that. Like where they >> > compare their results to an actual galaxy. >> >> What completely baffles me is your stark >> unwillingness to look at the generic features of the >> expected rotation curves, and the observed rotation >> curves. No actual discussion of how much mass is >> there is required. > > Excuse me? I am refusing to look? And I don't understand that a > rotation curve depends on mass to keep the system bound? > >> >> Rotation curves are direct observables. The interpretation >> >> does depend on mass to luminosity ratios, which are >> >> ALSO observables. It isn't as if what the paper does is >> >> controversial to your position. >> >> > It is the method used. Just as I told you. >> >> Yeah, you don't like the method. > > There are a number of methods. They mentioned them. > >> Do you have an argument that isn't the scientific >> equivalent of parents who think vaccines give kids >> autism? > > Do you have an argument at all, even one that clearly states that you > accept Dark Matter hook, line, and sinker, even though no cosmology > provides for production of the entirely invisible? Cosmology doesn't have a means to produce the baryons that build what we see, either. The prevalence of matter over antimatter is an unsolved problem. Try to keep that in mind. > Even though we > have detected normal matter that we cannot observe without an X-ray > source behind it? Hardly a strong argument. What you propose would scream in the EM like a goddamn nuke going off at night. There is no possible way we could not see it. > > Sure, you are in a fine camp. Lots of people accept that M/L based on > experimentally indistinguishable choices, can eliminate or increase > the amount of Dark Matter required. Except you are wrong. There is flexibility in what is required as the answer is model dependent, but the rotation curves have to be replicated. Which basic Newtonian theory will tell you requires a lot of matter where none is seen. You require dark matter whether you realize it or not, the only question is 'how much?'. This is why I know you haven't looked at the rotation curves and seriously thought about what you are seeing. > >> >> You just have to explain how to fill in that rather substantial >> >> amount of dark matter with normal matter while still playing >> >> by the observed rules of electromagnetism and gravitation. >> >> > Done. Even described in that paper. >> >> >> > or gravitational lensing (which we both know matter alone >> >> > can do, and highly ionized "sparse" normal matter is Dark >> >> > for visible light and less energetic observations), I'd love to >> >> > hear about it. >> >> >> Except normal matter isn't dark for the entire electromagnetic >> >> spectrum. Just some of it. Like has already been discussed. >> >> > Yep. We have to have a known x-ray source behind a region, >> > in order to see it. Those are fairly rare. >> >> Except in, once again, the bullet cluster which is lit up like >> a goddamn Roetgen christmas tree. Dark matter remains dark. > > The "tree" is in the center. You've already acknowledged we can > neither see the Dark Matter, nor the stars in those two galaxies... on > either side of it. Uh...this again? Just because a star is far away does not mean it is invisible, just that it is a point source. All those point sources blurred together form what we see, in addition to scattering off dust. > > So there is nothing to support either case in the Bullet Cluster. Are you being deliberately retarded? Baryonic matter would glow. Wholly ionized matter would scatter light and induce other observable effects, on top of whatever would be required to do ionize it in the first place. That, of course, doesn't even begin to cover the observational fact that the dark matter in the bullet cluster is not self-interacting while bulk amounts of like charges _ARE_ massively self-interacting. > >> >> > I expressed a desire to know "how it was done", and I >> >> > found a paper that describes that. It neither agrees with >> >> > me (even though it describes an M/L-based model that >> >> > needs no Dark Matter except outside the visible disk), >> >> >> Uh, that doesn't mean as much as you think. It takes a lot >> >> of matter to flatten out the rotation curves on the edge of a >> >> galaxy. >> >> > *And* we can in some cases see such normal matter. >> >> Really, enough normal matter to completely remove the >> need for dark matter? > > How do you know there isn't? That there are literally no signs of it in the electromagnetic spectrum. > The "missing normal matter" was much > greater than the amount of normal matter we could identify at one > time. > >> >> > nor does it disagree with you. It just drops >> >> > markers in the space I was interested in investigating. >> >> >I thought *you* might be interested in knowing too. >> >> >> > As to Dark Matter: >> >http://arxiv.org/abs/1005.4688 >> >> > I wonder how you get "turbulence" with a strong Dark >> >> > Matter component, neutrinos or not? >> >> >> No idea. I don't run the hydrocode simulations, or study >> >> them in sufficient detail. >> >> > Let me save you time. You cannot get turbulence >> > without friction. You cannot get friction with Dark Matter, >> > even neutrinos. >> >> Just a thought, but perhaps you could read the paper >> instead of guessing? The turbulence specifically refers >> to the behavior of normal matter. > > Yes, thank you. See above where I said "cannot have a strong Dark > Matter component"? Turbulence = friction = normal matter Read the paper instead of guessing. The context was specifically that of the baryonic matter. > > David A. Smith
From: dlzc on 3 Jul 2010 22:50 Dear eric gisse; On Jul 3, 2:13 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: > dlzcwrote: > > Dear eric gisse: > > > This topic is on topic in sci.astro. Leave it in the list of > > newsgroups. If you have the "nuts" to post on sci.astro, don't alter > > the Followup-to to remove it. > > Feature of the newsreader that I don't care enough to adjust. > Followups get set to the newsgroup I read this in. > > It remarkably cuts down on the bullshit resulting from people > who crosspost to 500 groups. > > > On Jul 2, 2:17 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: > >>dlzcwrote: > >> > On Jun 30, 5:24 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: > >> >>dlzcwrote: > >> >> > On Jun 30, 12:04 pm, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: > >> >> >>dlzcwrote: > >> >> >> >http://arxiv.org/abs/1005.3154 > > >> >> >> > Provides a lot of background into how Dark Matter > >> >> >> > is arrived at (as a free parameter, whose spatial > >> >> >> > distribution is far from simple, depending on the > >> >> >> > M/L modelled internal to the target galaxy). > > >> >> >> You do know that's not the only evidence for dark > >> >> >> matter, right? > > >> >> > Lest we go through your list of "evidence", what you > >> >> > have supplied to date can be done with simply normal > >> >> > matter. > > >> >> Not if you believe in electromagnetic theory. You require > >> >> some very special pleads to make bulk amounts of > >> >> hydrogen invisible, especially in *this* galaxy where radio > >> >> isn't redshifted into oblivion. > > >> > "Heliosheath". > > >> A region whose density is measured in atoms per > >> cubic meter, > > > And yet is sufficient, given a choice of M/L model. > > Pretend the galaxy is a sphere that's 125,000 light years wide. > > Estimates of the dark matter bulge are comfortably nestled > in the region of 2x10^12 solar masses, while in comparison > the mass of what's directly observable is in the region of > 10^10 solar masses. What is*directly* observable is 'an" order of magnitude less than this. That is the "sin" committed by M/L. We accept that there is 'some' normal matter that we cannot see. And we assume that ratio is the same across the galaxy. > 125,000 light years is ~10^21 m. The volume for that sphere > is ~2x10^63 m^3. > 2x10^12 solar masses = 4x10^42 kg > 1 kg of hydrogen = 1000 moles = 6x10^26 atoms > > so 2x10^12 solar masses ~ 10^69 atoms > > That many atoms of hydrogen in that 125,000 light year sphere > would require an _average_ density of about 10^6 atoms/m^3 > which is an order of magnitude or 6 higher than the average > density of vacuum. Not in the Milky Way. We average nearly 1 particle per cc, or 10^6 particles per m^3. > Which is, in turn, a massive underestimate because I assumed > the galaxy was a sphere. Dark Matter is roughly allocated as an oblate sphere, if Andromeda is any guide. > Add another factor of 15 or so if you want a number closer > to reality. > > IT CAN NOT WORK. DO YOU SEE YET? You can DOUBLE > the effective size of the galaxy and you will still be orders of > magnitude off. Actually, no. Your own numbers indicate that the interstellar gases alone could do it. > >> > Plenty of bulk hydrogen available, and invisible until > >> > it is braked. > > >> Unless you point a radio telescope at the 21cm line, > >> which neutral hydrogen radiates at. Or talk to an > >> astronomer about the general irritant which interstellar > >> hydrogen poses to observations at the galactic center. > > > I'm refering to the ionized stuff, and you know that. > > Except the traversal of electromagnetic waves through a > plasma leaves rather significant tell tale signs. The drift > velocity of bulk anything about a galaxy will induce > massive faraday rotation in electromagnetic waves, > because you demand a wholly ionized plasma of a > significant amount of hydrogen. Doesn't work unless you have recombination. Once hydrogen loses the one electron... > That we don't see such polarization in the CMB, or > evidence of Compton scattering off all those bulk > electrons that are required, is rather telling. No, its not at all telling. > And review basic electromagnetic theory. You are > essentially demanding that 10^12 solar masses > worth of separated charge - where's the energy coming > from to maintain that separation? At tens of millions of degrees, its no problem. You know its there. You yourself have cited the values. > Hmm, how much energy would that be? Hydrogen's > binding energy is 13.6 eV, so you'll need 6x10^26 * > 13.6eV = 8x10^27 eV worth of energy expended to do > that. Any guesses as to where that energy is coming > from, and how frequently it needed to be expended? None at all, if it never recombines. And it is still zipping along from the supernova or Big Bang that launchd it. > >> > And we also (purportedly) are in a sparsely populated > >> > portion of the galaxy... > > >> >> > If you have something > >> >> > other than rotation curves (which this paper says > >> >> > uses M/L) > > >> >> What the paper actually says is the following: > > >> >> We assume that the rotation curve V(R) of the disk > >> >> galaxy, for which we want to construct a > >> >> mass model, is known (i.e., it has been > >> >> ?observed?); as a mathematical boundary > >> >> condition, we assume that the rotation > >> >> curve remains flat at V_\infty out to infinite > >> >> radii. > > >> > They say a lot more than that. Like where they > >> > compare their results to an actual galaxy. > > >> What completely baffles me is your stark > >> unwillingness to look at the generic features of the > >> expected rotation curves, and the observed rotation > >> curves. No actual discussion of how much mass is > >> there is required. > > > Excuse me? I am refusing to look? And I don't understand that a > > rotation curve depends on mass to keep the system bound? > > >> >> Rotation curves are direct observables. The interpretation > >> >> does depend on mass to luminosity ratios, which are > >> >> ALSO observables. It isn't as if what the paper does is > >> >> controversial to your position. > > >> > It is the method used. Just as I told you. > > >> Yeah, you don't like the method. > > > There are a number of methods. They mentioned them. > > >> Do you have an argument that isn't the scientific > >> equivalent of parents who think vaccines give kids > >> autism? > > > Do you have an argument at all, even one that clearly > > states that you accept Dark Matter hook, line, and sinker, > > even though no cosmology provides for production of the > > entirely invisible? > > Cosmology doesn't have a means to produce the baryons > that build what we see, either. The prevalence of matter > over antimatter is an unsolved problem. > > Try to keep that in mind. Try and explain how neutrinos that are produced with high energies, get cooled enough to be gravitationally captured. > > Even though we > > have detected normal matter that we cannot observe without > > an X-ray source behind it? > > Hardly a strong argument. What you propose would scream in > the EM like a goddamn nuke going off at night. But it doesn't. The density isn't high enough. > There is no possible way we could not see it. We can't. We don't. We can only see these huge volumes of mass, because the oxygen is missing five electrons. > > Sure, you are in a fine camp. Lots of people accept that > > M/L based on experimentally indistinguishable choices, can > > eliminate or increase the amount of Dark Matter required. > > Except you are wrong. It is in the paper cited, and it was reporting other's papers. > There is flexibility in what is required as the answer is model > dependent, but the rotation curves have to be replicated. Which > basic Newtonian theory will tell you requires a lot of matter where > none is seen. You require dark matter whether you realize it or > not, the only question is 'how much?'. No, *I* don't require *any* Dark Matter. > This is why I know you haven't looked at the rotation curves and > seriously thought about what you are seeing. I have. M/L makes your imaginary mistake for you. > >> >> You just have to explain how to fill in that rather substantial > >> >> amount of dark matter with normal matter while still playing > >> >> by the observed rules of electromagnetism and gravitation. > > >> > Done. Even described in that paper. > > >> >> > or gravitational lensing (which we both know matter alone > >> >> > can do, and highly ionized "sparse" normal matter is Dark > >> >> > for visible light and less energetic observations), I'd love to > >> >> > hear about it. > > >> >> Except normal matter isn't dark for the entire electromagnetic > >> >> spectrum. Just some of it. Like has already been discussed. > > >> > Yep. We have to have a known x-ray source behind a region, > >> > in order to see it. Those are fairly rare. > > >> Except in, once again, the bullet cluster which is lit up like > >> a goddamn Roetgen christmas tree. Dark matter remains dark. > > > The "tree" is in the center. You've already acknowledged we can > > neither see the Dark Matter, nor the stars in those two galaxies... on > > either side of it. > > Uh...this again? Just because a star is far away does not mean it is > invisible, just that it is a point source. All those point sources blurred > together form what we see, in addition to scattering off dust. The dust was left behind. No blur. Give up on the Bullet Cluster. > > So there is nothing to support either case in the Bullet Cluster. > > Are you being deliberately retarded? Stick it in your ear. *plonk* David A. Smith
From: Yousuf Khan on 4 Jul 2010 06:32 On 7/4/2010 2:35 AM, eric gisse wrote: > Yousuf Khan wrote: > >> On 7/3/2010 6:49 AM, eric gisse wrote: >>> Turbulence typically refers to self-interactions within a fluid. I'm >>> pointing out the specific exception now rather than having to point out >>> later and then deal with 'but you said there's no turbulence!!!!' >>> response. >>> >>> Its' like people aren't listening when I say dark matter is modeled as a >>> perfect fluid. What the hell do folks think that implies? >> >> Then it's not a perfect fluid if there are self-interactions. You can >> say it's *close* enough to a perfect fluid at the galactic scale. At >> bigger scales, it is not. Second of all, you do realize that all of >> these "if...then...but if...else..." type behaviours of Dark Matter is >> exactly what Dark Fluid is supposed to address. >> >> Yousuf Khan > > The gravitational self-interactions do not appear in the stress tensor that > describes it. That's why it is a perfect fluid. Which is probably why DM can't explain the Train Wreck Cluster. Yousuf Khan
From: Yousuf Khan on 4 Jul 2010 07:49
On 7/4/2010 1:24 AM, dlzc wrote: > Do you have an argument at all, even one that clearly states that you > accept Dark Matter hook, line, and sinker, even though no cosmology > provides for production of the entirely invisible? Even though we > have detected normal matter that we cannot observe without an X-ray > source behind it? > > Sure, you are in a fine camp. Lots of people accept that M/L based on > experimentally indistinguishable choices, can eliminate or increase > the amount of Dark Matter required. Just to play devil's advocate for a moment, but if there's so much matter that only can be seen through X-ray absorption, then why aren't we seeing it within our own galaxy, where there should be plenty of X-ray sources lighting up the sky, at least from within the galactic disk? Yousuf Khan |