I Questions regarding dark matter dynamics (1 Viewer)

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Hi Michael:

The following is another, and a more clearly written, discussion of the relationship between Deuterium and dark matter.
Here is a pertinent quote:
During the formation of helium nuclei, perhaps only one in 10,000 deuterons remained unpaired. An even smaller fraction fused into nuclei heavier than helium, such as lithium. (All the other familiar elements, such as carbon and oxygen, were produced much later inside stars.) The exact percentages of helium, deuterium and lithium depend on only one parameter: the ratio of protons and neutrons--particles jointly categorized as baryons--to photons. The value of this ratio, known as n (the Greek letter eta), remains essentially constant as the universe expands; because we can measure the number of photons, knowing n tells us how much matter there is. This number is important for understanding the later evolution of the universe, because it can be compared with the actual amount of matter seen in stars and gas in galaxies, as well as the larger amount of unseen dark matter.​

For the big bang to make the observed mix of light elements, n must be very small. The universe contains fewer than one baryon per billion photons. The temperature of the cosmic background radiation tells us directly the number of photons left over from the big bang; at present, there are about 411 photons per cubic centimeter of space. Hence, baryons should occur at a density of somewhat less than 0.4 per cubic meter. Although cosmologists know that n is small, estimates of its exact value currently vary by a factor of almost 10. The most precise and reliable indicators of n are the concentrations of primordial light elements, in particular deuterium. A fivefold increase in n, for example, would lead to a telltale 13-fold decrease in the amount of deuterium created.​

Regards,
Buzz
These types of calculations are very interesting and useful, and IMO they should be used to either falsify or verify LCDM. I would say that *if* we knew from controlled laboratory experimentation that exotic forms of matter definitely exist in nature, then such a technique might be very useful in estimating the ratio of each type of matter (dark/baryonic) that might actually exist in space.

Since we have ample evidence to suggest that the baryonic mass estimates of galaxies that we've been using are seriously innaccurate, I'm hesitant to leap to any conclusion which constricts me and *obligates* me to any specific ratio of exotic matter in the universe. How do I even know for certain that exotic forms of matter even exists at all from uncontrolled observations in space and galaxy mass estimates which are not correct? If we start assuming that a very specific ratio of exotic matter to normal matter *must* exist and therefore we *assume* that exotic forms of matter *must* exist, I think it's very easy to get lost in 'dogma' and locked into a particular dogma rather than being up front about the current limits of our technology and the serious and numerous problems in our baryonic mass estimation techniques.

If exotic forms of matter do not exist in nature, then LCDM should be falsified and die by that same prediction sword if it cannot explain the elemental abundance figures without exotic 'fudge factors".

Let's take a close hard look at the various laboratory experiments over the past decade. We have literally spent billions of dollars/euros "testing" the standard particle physics model at LHC, and thus far it's performed flawlessly. We've also tested several non standard particle physics models like SUSY theory, and they've come up empty at LHC. Not a single 'sparticle" has been observed, and LHC is now operating at close to it's maximum energy state. We've also spent many millions of dollars at LUX and PandaX and Xenon100 and now Xenon1T experiments which have all tried and failed to find direct laboratory evidence for exotic forms of matter, The results to date of every single lab experiment related to exotic matter have all been all negative.

https://en.wikipedia.org/wiki/Plasma_cosmology#Alfv.C3.A9n.E2.80.93Klein_cosmology
http://www.nytimes.com/1989/02/28/science/novel-theory-challenges-the-big-bang.html?pagewanted=all

If you set aside any need for creation (of matter) concepts for a moment there is no evidence that exotic forms of matter exist. Hannes Alfven for instance proposed a cyclical type of "bang' theory that was based upon matter/antimatter interaction. His theory did not require that all matter in the universe was ever required to condense itself to a single "point' before matter/antimatter interactions began to cause it to expand again. It may have only contracted to say 10 percent of it's current size before expanding again. In such a scenario, the elemental composition of the universe today might have more to do with the original elemental composition prior to 'contraction' and less to do with with anything related to the annihilation or 'expansion' process.

A couple of other tidbits of information that may be noteworthy here are the fact that the various stellar underestimation problems which I cited earlier would tend to suggest that a significant portion of the 'missing mass' from that 2006 Bullet Cluster lensing study is likely to be found inside of stellar mass, and probably also in neutral hydrogen gas that would tend to "pass on through" a galaxy collision process. Because of various EM influences, the hot plasma halos around galaxies are more likely to "collide" in cluster collisions, but the distance between stars in any given galaxy minimize the likelihood that stars would actually physically collide very often in a 'collision' process. That type of dense matter would tend to pass right through, as would neutral atoms of dust and non plasma. The hot plasma halo tends to perform more like a "fluid" and it would be more inclined to interact and collide.

The current standard solar model predicts stellar abundance figures which are based upon the concept of 'fast" solar convection processes which presumably keep heavier elements like Nickel and Iron mixed together with wispy light elements like Hydrogen and Helium, from deep within the sun at the base of the convection zone, all the way up to the surface of the photosphere.

https://scitechdaily.com/unexpectedly-slow-plasma-flow-measured-below-the-suns-surface/

SDO measurements in 2012 revealed that contrary to 'jet speed' convection predictions of the standard solar model, SDO measured something closer to walking speed convection inside of the sun. How that "slow" convection process might affect stellar abundance figures is anyone's guess, and I would therefore hate to obligate myself to any specific elemental abundance figures at the moment.
 
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Hi Michael:

I looked at your first link to the 2008 paper and wondered whether that would fit with the paper from Magain, P. and Chantry, V. (2013), which I mentioned earlier in this thread, looking at Einstein rings from early galaxies and finding an error of factor of 1.8 between observed mass by luminosity and lensing mass. I thought both methods were robust and the difference due to non-radiating baryonic matter.

Adrian.
I'm falling behind on my reading at the moment but I'll try to catch up tomorrow. I'll just say at the moment that I'm comfortable with and confident in the mass calculations of galaxies that are based upon lensing techniques and galaxy rotation patterns, but I'm equally confident that our baryonic mass estimation techniques need a serious revision in light of the various discoveries of the past decade. My first instinct would be to presume that any and all 'missing mass' is likely to be found in ordinary plasma/hydrogen halos or ordinary dust, or ordinary stars rather than anything particularly exotic in nature. The two different mass halos that have been discovered (or at least better quantified) over the last five years might very well go a long way to explain our current dark matter halo models.
 
Hi Michael:

I am not sure I understand this. What does "plasma mass" mean here? Is it the mass of baryonic matter in a plasma state prior to the time when the universe has cooled and the state changes from plasma to gas? If so, what does "core mean? I am confused since I understood that "dark matter" halo models were about the formation of galaxies (or perhaps galactic clusters) at a time long after the plasma state of the universe.

Regards,
Buzz
My reference to the term core relates to the core of galaxies. All of my comments were related to current lensing studies and/or galaxy rotation patterns *in general*, not cosmology theory per se.

Two of the references on my list were related to the discovery of both a plasma halo and a neutral hydrogen halo that surround our galaxy. Our current models of dark matter distribution would 'predict" that the stars in every galaxy are surrounded by a "halo" of mass that contains more mass than all the stars in the galaxy.

https://en.wikipedia.org/wiki/Dark_matter_halo

Indeed we find that our own galaxy is surrounded by both a halo of hot plasma, and halo of cooler neutral hydrogen atoms:

http://chandra.harvard.edu/blog/node/398
https://cosmosmagazine.com/space/galaxy-s-hydrogen-halo-hides-missing-mass

I seriously doubt that it's a coincidence that the dark matter halo models look to coincide with the mass layout patterns that we're now discovering around our own galaxy in the form of ordinary baryonic matter that we simply didn't "see/observe" until recently.
 

Buzz Bloom

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Does that help? An order of magnitude range sounds like "dark matter may or may not be there".
Hi stefan:

The article I quoted is relatively old, I believe it is also from the 1990s, and I believe the factor of 10 referred to the state of estimating eta before reliable astronomical measurements of Deuterium became available. There are much better estimates now, although you have pointed out that you are not satisfied that the modern values are reliable.

The quote was intended to explain the concept of the relationship between Deuterium and dark matter, and that this is an alternative way of estimating eta and from that estimating the ratio between baryonic and dark matter. Later in the article there is a discussion of improvements in the ability to measure Deuterium that had happened between the 70s and 90's.

Here is another quote I think you must gave missed.
The mere presence of deuterium sets an upper limit on n because the big bang is probably the primary source of deuterium in the universe, and later processing in stars gradually destroys it.​
This means that even before measuring how much deuterium is there, the fact that it is there at all places a lower limit on eta.

Regards,
Buzz
 

Buzz Bloom

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I seriously doubt that it's a coincidence that the dark matter halo models look to coincide with the mass layout patterns that we're now discovering around our own galaxy in the form of ordinary baryonic matter that we simply didn't "see/observe" until recently.
Hi Michael:

As I have been discussing with stefan, the estimate of the ratio of baryonic matter to all matter includes the estimate of the photon to baryon ratio, η, and the astronomical measurements of the abundance of Deuterium. This is an independent estimate from that based on the observed relationship of star velocities with their distance from a galactic core.

Regards,
Buzz
 
I'm frankly a little apprehensive about "assuming" the existence of exotic forms of matter only to make sure that LCDM mathematically "fits' some other completely different observation. I'd probably feel differently were it not for all the negative results from the various dark matter "tests" at LHC, LUX, PandaX, Xenon100,and even recent Xenon-1T results. As it stands, the nucleosynthesis argument seems more like a case of special pleading, only so that LCDM can be considered exempt by falsification by the non-existence of exotic forms of matter.
It appears that you don't know how historically dark matter theory came to be.

At first, astronomers and cosmologists did assume that baryonic matter is all that there is.

A few observations (in 1930-40) which claimed to maybe detect discrepancies, were ignored - which is ok, since there are _always_ some observations which find "something strange", but these may well be instrument errors or mistaken interpretation or logic of their authors.

Then Vera Rubin in 1970s worked on galaxy rotation curves and found that galaxies seem to be heavier than they should be. Her work was high-quality and was checked by other independent measurements, but still, science did not jump on dark matter bandwagon overnight. The status shifted to "hmmm, there is indeed something fishy here! Let's look at it more carefully!"

The entire 1980s were spent doing more observations, looking at several disjoing pieces of evidence, and all of them pointed quite consistently to the conclusion that baryonic mass alone is far from being enough to explain them.

Since you don't remember this long and convoluted process of history, you seem to assume everybody just happily fudges their models and observations to satisfy their preconceived notion that "dark matter exists"?
 
It appears that you don't know how historically dark matter theory came to be.
Actually I would argue that the reverse is true because I'm old enough to remember when the term "dark matter" didn't necessarily imply exotic forms of matter. I think it was Fritz Zwicky who first coined the term. Originally it didn't automatically imply an exotic type of matter however.

At first, astronomers and cosmologists did assume that baryonic matter is all that there is.
Sure, and they do in fact have observations and "galaxy mass estimations" that don't seem to jive. That conflict between observation and baryonic mass estimation could be related to almost anything, including errors in our baryonic mass estimates, which is likely considering the revelations of the past decade.

A few observations (in 1930-40) which claimed to maybe detect discrepancies, were ignored - which is ok, since there are _always_ some observations which find "something strange", but these may well be instrument errors or mistaken interpretation or logic of their authors.

Then Vera Rubin in 1970s worked on galaxy rotation curves and found that galaxies seem to be heavier than they should be. Her work was high-quality and was checked by other independent measurements, but still, science did not jump on dark matter bandwagon overnight. The status shifted to "hmmm, there is indeed something fishy here! Let's look at it more carefully!"

The entire 1980s were spent doing more observations, looking at several disjoing pieces of evidence, and all of them pointed quite consistently to the conclusion that baryonic mass alone is far from being enough to explain them.
Somewhere between the early 70's and 2006 the term however gradually "morphed" from being synonymous with "we don't know what that missing mass is made of", to being associated with an exotic type of matter. I don't have any doubt that there is evidence of 'missing mass' from galaxy mass estimation techniques, but I have no evidence to suggest that any of that missing mass is to be found in exotic types of matter, and in fact I have no laboratory evidence that exotic forms of matter even exist in nature.

Since you don't remember this long and convoluted process of history, you seem to assume everybody just happily fudges their models and observations to satisfy their preconceived notion that "dark matter exists"?
I think you misunderstand my position. I have no doubt that there is a 'missing mass' problem which could be related to just about anything, including serious mass estimation problems with our galaxy mass estimation models. There does seem to be *ample* evidence that we've simply been underestimating the amount of ordinary plasma that is present in various galaxies. We didn't even know about the existence of that hot plasma halo, or that cooler hydrogen halo around our own galaxy until quite recently in fact.
 
Hi Michael:

As I have been discussing with stefan, the estimate of the ratio of baryonic matter to all matter includes the estimate of the photon to baryon ratio, η, and the astronomical measurements of the abundance of Deuterium. This is an independent estimate from that based on the observed relationship of star velocities with their distance from a galactic core.

Regards,
Buzz
I realize that it's an independent estimate from lensing studies, and independent from galaxy rotation pattern studies, but as I pointed out before, the Alfven-Klein expansion model does not predict that all matter was ever as concentrated as you seem to believe. It could be that the various elemental abundance figures that we see today are in no way related to a 'big bang" event, but those ratios may simply relate back to the abundance of elements that existed *before* expansion. I can't just "assume" that A) exotic matter exists, and B) it makes up X percent of the universe based on that technique.
 
I think you misunderstand my position. I have no doubt that there is a 'missing mass' problem which could be related to just about anything, including serious mass estimation problems with our galaxy mass estimation models.
Ok.

There does seem to be *ample* evidence that we've simply been underestimating the amount of ordinary plasma that is present in various galaxies. We didn't even know about the existence of that hot plasma halo, or that cooler hydrogen halo around our own galaxy until quite recently in fact.
The cooler halo: you classified it as "in 2012, we 'discovered' more ordinary baryonic matter *surrounding* every galaxy that exist inside of the stars themselves", but the paper you refer to estimates it to weigh about 1.5-2% of Galaxy's mass (see my post #11 in this thread). It seems to me that you are reading too much from pop-sci descriptions, which tend to hyperbolize.
 

Bandersnatch

Science Advisor
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In addition to rotation curves, Bullet cluster, and nucleosynthesis, there's also the power spectrum of baryon acoustic oscillations, which so far I haven't seen mentioned in this thread - despite being the least burdened with uncertainties.
This means there are four independent data points, all suggesting the same conclusion, which is what makes DM such a strong hypothesis.
 
The cooler halo: you classified it as "in 2012, we 'discovered' more ordinary baryonic matter *surrounding* every galaxy that exist inside of the stars themselves", but the paper you refer to estimates it to weigh about 1.5-2% of Galaxy's mass (see my post #11 in this thread). It seems to me that you are reading too much from pop-sci descriptions, which tend to hyperbolize.
When they only have identified about 2 percent of the matter in the galaxy, finding another 2 percent is a "large change". As I pointed out, they were comparing the amount of known stellar mass to the amount of mass they found, and it was quite comparable to the known stellar mass of the galaxy. Keep in mind that this is *in addition to* all the other baryonic mass they found recently a neutral hydrogen halo surrounding the galaxy.

https://cosmosmagazine.com/space/galaxy-s-hydrogen-halo-hides-missing-mass
 
When they only have identified about 2 percent of the matter in the galaxy, finding another 2 percent is a "large change". As I pointed out, they were comparing the amount of known stellar mass to the amount of mass they found, and it was quite comparable to the known stellar mass of the galaxy.
You are backtracking now. You did not say "comparable", you said:
"we 'discovered' more ordinary baryonic matter *surrounding* every galaxy that exist inside of the stars themselves".

10 billion solar masses of gas claimed in the paper is not more than all stellar mass in Milky Way. It's much less.
There are different estimates of the latter, but they are all above 40 billion solar.
Example: https://arxiv.org/pdf/1102.4340.pdf estimates total stellar mass in MW to be 64+-6 billion solar.
 
In addition to rotation curves, Bullet cluster, and nucleosynthesis, there's also the power spectrum of baryon acoustic oscillations, which so far I haven't seen mentioned in this thread - despite being the least burdened with uncertainties.
This means there are four independent data points, all suggesting the same conclusion, which is what makes DM such a strong hypothesis.
Let's take a close look at those four data points:

We have a Bullet Cluster study that is known to be *riddled* with baryonic mass underestimation problems.

We have galaxy mass estimation/rotation models that also suffer from the same mass halo underestimation problems as the Bullet Cluster study.

We have a potential *falsification* mechanism for LCMD theory with respect to nucleosynthesis requirements of exotic forms of matter for which we have no laboratory evidence whatsoever, even after spending billions of dollars looking for it.

Finally we have BAO estimates which also do not work *without* the need for exotic forms of matter and energy so we have two potential falsification methods for one specific cosmology theory, specifically LCDM. Both the nucleosythesis and BAO numbers seem to work out to the same ratio of exotic vs. baryonic matter which could be used as possibly *two* different remaining data points of evidence, but they could both be falsified in the absence of exotic forms of matter and we have no evidence from the lab that exotic forms of matter exist in nature.

I'd grant you two independent data points in 2017, but not 4. :)
 
You are backtracking now.
Well, I've already admitted that my use of the term "more" was potentially a tad misleading, and that word was worth backtracking from, but you still seem to be using a single number related to their findings, whereas they actually suggested that your 10 billion solar mass estimate was just a low end starting point and the actual number could be significantly higher:

http://www.urban-astronomer.com/news-and-updates/milky-way-surrounded-by-hot-gas/

Astronomers estimate the temperature of this hot gas at between 1 and 2.5 million Kelvins, or several hundred times hotter than the surface of the Sun. It is also huge, containing a mass of gas of at least 10 billion Suns, and possibly as much as 60 billion Suns.
Emphasis mine.

You did not say "comparable", you said:
"we 'discovered' more ordinary baryonic matter *surrounding* every galaxy that exist inside of the stars themselves".

10 billion solar masses of gas claimed in the paper is not more than all stellar mass in Milky Way. It's much less.
There are different estimates of the latter, but they are all above 40 billion solar.
Example: https://arxiv.org/pdf/1102.4340.pdf estimates total stellar mass in MW to be 64+-6 billion solar.
Their top end figure is significantly higher than 40 billion solar masses (it's 60), so in theory at least my use of the term "more" could be correct, but admittedly it's an "optimistic" (and subjective) assessment on my part. If your 70 solar mass number is correct, their 60 billion solar mass top end is still very comparable to all the baryonic mass that we had found prior to 2012.
 
Their top end figure is significantly higher than 40 billion solar masses (it's 60), so in theory at least my use of the term "more" could be correct, but admittedly it's an "optimistic" (and subjective) assessment on my part. If your 70 solar mass number is correct, their 60 billion solar mass top end is still very comparable to all the baryonic mass that we had found prior to 2012.
Wrong. 64+-6 billion solar masses is not the estimate of all baryonic mass in Milky Way. It's estimate of _mass of stars only_. I'm sure you know that we _know_ (for at least a century) that stars are not the only baryonic mass in MW.
Total MW mass estimates are 500-800 billion.
 
requirements of exotic forms of matter for which we have no laboratory evidence whatsoever, even after spending billions of dollars looking for it.
Those very same experiments also fail to detect one form of matter - neutrinos - which we are 100.00% sure exist. Therefore, non-observation (so far) of dark matter is not a strong argument against it.
In fact, many theories posit that DM is nothing else than new types of neutrino (say, right-handed neutrinos with Majorana masses).
 
Wrong. 64+-6 billion solar masses is not the estimate of all baryonic mass in Milky Way. It's estimate of _mass of stars only_. I'm sure you know that we _know_ (for at least a century) that stars are not the only baryonic mass in MW.
Total MW mass estimates are 500-800 billion.
Let's be specific. I was specifically comparing the amount of baryonic mass that they found in 2012 with the baryonic mass they'd discovered prior to 2012. If we use a 600 billion solar mass total, and divide that number by 6 because "dark matter" is presumed to be five times more abundant than baryonic mass, that's around 100 billion solar masses of baryonic mass total that is predicted to exist in our galaxy in LCDM theory. Of that total, only between 40 and 60 billion solar masses are concentrated in stars, and the rest is typically described as the "missing baryon" problem. Both of the "halo" papers were specifically describing that "missing baryon" mass, and it's presumed to be about half of the total baryonic mass. We're talking about comparing stellar baryonic mass, to a "plasma halo" mass that contains somewhere between 10 and 60 billion solar masses.

My original statement may have been a little "optimistic" by my use of the term "more", but either way, the authors did suggest that the they'd found the missing baryonic mass that we haven't accounted for yet.

Now of course there is not only a "hot plasma" halo that's been discovered since 2012, there's also a "neutral hydrogen" gas halo that's also been discovered and expected to also hold a tremendous amount of mass.

If anything, there isn't a "missing baryon problem" anymore, there's potentially an *excess baryon problem* when we add in both halo masses. Mind you that's all in addition to all the satellite galaxies that we keep discovering around our galaxy every year.

http://www.blastr.com/2017-2-23/astronomers-discover-new-satellite-milky-way
 
Those very same experiments also fail to detect one form of matter - neutrinos - which we are 100.00% sure exist. Therefore, non-observation (so far) of dark matter is not a strong argument against it.
In fact, many theories posit that DM is nothing else than new types of neutrino (say, right-handed neutrinos with Majorana masses).
There are however other experiments which were/are specifically designed upon the mathematical predictions of neutrino theory rather than WIMP or Axion theory which do detect neutrinos. There really isn't any known evidence to support other types of neutrinos either based on neutrino detector data.

http://www.latimes.com/science/sciencenow/la-sci-sn-icecube-sterile-neutrino-20160809-snap-story.html

Neutrinos would also tend to be "hot dark matter", as opposed to "cold dark matter", and I have no idea how that might effect either the nucleosynthesis predictions of LCMD, or the BAO predictions.
 
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In any conversation about dark matter, it is only a matter of time before the Bullet Cluster makes an appearance. However, reading some recent reports it is far from clear that the Bullet Cluster is a good piece of evidence for or against dark matter. A couple of early papers from 2010 and 2011 suggested that the in-fall velocity was too high to support ΛCDM. A more recent paper by Craig Lage and Glennys R. Farrar published 25 February 2015 in Journal of Cosmology and Astroparticle Physics, concluded “due to the paucity of examples of clusters with such a high mass in simulations, these features of the main cluster cannot presently be used to test ΛCDM.”
 
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It appears that you don't know how historically dark matter theory came to be.

At first, astronomers and cosmologists did assume that baryonic matter is all that there is.

A few observations (in 1930-40) which claimed to maybe detect discrepancies, were ignored - which is ok, since there are _always_ some observations which find "something strange", but these may well be instrument errors or mistaken interpretation or logic of their authors.

Then Vera Rubin in 1970s worked on galaxy rotation curves and found that galaxies seem to be heavier than they should be. Her work was high-quality and was checked by other independent measurements, but still, science did not jump on dark matter bandwagon overnight. The status shifted to "hmmm, there is indeed something fishy here! Let's look at it more carefully!"

The entire 1980s were spent doing more observations, looking at several disjoing pieces of evidence, and all of them pointed quite consistently to the conclusion that baryonic mass alone is far from being enough to explain them.

Since you don't remember this long and convoluted process of history, you seem to assume everybody just happily fudges their models and observations to satisfy their preconceived notion that "dark matter exists"?
I think you answered a different question. My interpretation is that Michael was suggesting care was needed in using CDM to answer problems about Deuterium abundance when CDM is still hypothetical until a definite candidate for CDM is discovered.
 

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