View Full Version here: : Missing Mass Discovered
25-05-2011, 07:18 AM
Another Oz Astrophysics first from an undergraduate student !
Universe's not-so-missing mass (http://www.physorg.com/news/2011-05-universe-not-so-missing-mass.html)
oh no !
25-05-2011, 07:43 AM
I wouldn't start baking the humble pie just yet !:lol:
25-05-2011, 07:55 AM
Nothing humble in that pie, Adam.
25-05-2011, 10:56 AM
Good on her:):)
That's great to see undergrads get in on the action and actually contribute to our knowledge. Should happen more often.
25-05-2011, 11:22 AM
Sounds like Joclyne Bell all over again:)
Well done to her:thumbsup:
25-05-2011, 12:43 PM
So does this signal the death of Dark Energy and Matter?
25-05-2011, 12:50 PM
No, not by a long shot.
All they have done is added to the baryonic matter content and they'll have to revise the numbers, depending on how much there is. They'll also have to take this into account with the factor of 3 increase in the numbers of late class stars they've discovered recently.
25-05-2011, 01:01 PM
Take a look at the challenges being faced at present when trying to detect these intergalactic filaments:
- the densities of the structures predicted by models is expected to be in the range of 10^-6 to 10 ^-4 electrons per cubic centimetre.
- the temperatures are in the range of 10 ^5 to 10^7 K
- the path length of the filamentary structures detected to date, are in the order 10-14.6 Mpc in length!
These filaments must be close to infinite conductivity, and thereby resulting in giant intergalactic frozen-in magnetic fields ! ;)
What are the key detection methods ?..
This study used a not-thus-far-used data analysis technique, applied to the 2 degree Field Galaxy Redshift Survey (2dFGRS) and ROSAT All-Sky Survey data.
Why havent they been detected before ? ...
Great stuff ! Good on 'em.
Paper here. (http://arxiv.org/pdf/1104.0711v2)
25-05-2011, 01:03 PM
The 'missing mass discovered' title is a little misleading since Dark Matter and Energy were 'invented' to account for the 'missing mass' in the first place!
25-05-2011, 01:11 PM
From the paper ..
I think this refers to the baryonic component of the universe (which is pretty big chunk of the total baryonic mass eh) ?
I think the rough proportions are (today):
- dark matter ~ 23%;
- dark energy ~ 72%
- baryonic ~ 5%
PS: Gotta be careful .. these figures account for the mass-energy density of the observable universe only. In the bigger picture of the entire universe, to maintain the correct mass/energy density, they require about 83% DM, with ordinary matter being only about 17%.
25-05-2011, 01:14 PM
The dark matter isn't missing !
Its as real as dark energy !
25-05-2011, 01:18 PM
My understanding is that baryonic is a measure of what we can see and measure (about 5% of the total predicted mass of the universe) and the rest is 'dark' to account for the 'missing mass' required for physics to work as predicted!
So if we are finding 'missing mass' then this is in addition to the 5% already known. So for the more mass we find, the less the percentage of 'dark' - no?
25-05-2011, 01:23 PM
My God!!!!...don't let the sparkyboys know about this!!!:):P:P:P
They'll ignore the rest of the data and zero in on this:):P
25-05-2011, 01:26 PM
That's why I wrote before that they'll have to revise their numbers a bit to account for the new material. It's not going to make a big difference, nor will it substantially change the theory but it will mean more of the ordinary stuff is hanging around.
25-05-2011, 01:38 PM
As the detection methods improve I think they will find more and more Baryonic matter.
Carl do you think they are to rigid in their percentages of different matter as New Baryonic matter is being discovered quite ofton now :question:
25-05-2011, 01:38 PM
Thought you'd like that bit
They completely refuse to accept near-to infinite conductivity plasma, and frozen-in magnetic fields. (For secret, undisclosed reasons).
But take a look at the temperatures/densities these guys have measured ! If ever there was empirical data supporting primordial, intergalactic frozen-in magnetic fields, I would have thought this was it !?
I'll bet they'll see this article, and spin it in the 'usual' directions, though.
25-05-2011, 01:39 PM
Alternatively, is this the start of the detection of dark matter? Basically finding matter we were previously unable to see!
25-05-2011, 01:41 PM
This stuff was detected in the X-Ray spectrum !
.. Ie: they finally saw it !
'Twasn't dark enough !
(Ie: it emits/interacts in the EM spectrum).
25-05-2011, 01:48 PM
True, but what constitutes Dark Matter in 'theory' is just a hypothisis - so at the very basic level, anything that we previously could not detect but now can detect could in fact be what was previously known as dark matter!
25-05-2011, 02:24 PM
The percentages of baryonic to dark matter to dark energy are pretty fluid. It depends on who you talk to, but the accepted figures are fairly much in line with the theory. If more or less of any of the constituents are accounted for or discounted by theory and observation, they'll just change the figures.
25-05-2011, 02:29 PM
They'll have to go and consult Rocky and Bullwinkle (Peratt and Lerner) for their arcane deliberations on the matter:):P:P:P
"Oh great and all-knowing squirrel....wise and learned moose....":):P:P
25-05-2011, 02:34 PM
If you wanted to take a very broad definition of what constitutes "dark matter", then you would loosely be correct. But if you took dark matter to be what most physicists and astronomers commonly think of it as being (particles of matter that can't be detected by normals means and only interact with the rest of the universe by their gravitational influence) then you would be incorrect.
25-05-2011, 02:50 PM
Actually .. I might have to have more of a think about this. The temperature they've measured this stuff at, is pretty high. Its very low in density, spread out over huge volumes.
I think high conductivity plasmas are expected to be low in temperature and low in density.
I would think it might be difficult to describe the behaviours of these plasmas, as I would think there might not be much info at hand about them.
Hmm … :question:
Need more input !
25-05-2011, 02:52 PM
Thats like me saying I have $500.00 in the bank but if there is $520.00 I will just change the number:shrug:
The voids they have been talking about for ages are begining to find are not so empty.
Also thy are finding more and more Dwarf galaxies and other stufflike planets not related to stars ect.
25-05-2011, 03:10 PM
Yes, but the numbers are fluid. They'll change as they finesse the quantities of the matter/energy that they find. However, even if they found 10 times more baryonic matter than they know of now, it's still not going to change the percentages much. It would still be an order of magnitude too small to account for what they observe is going on. It wouldn't matter how many dwarf galaxies and such they found, there's just not enough of them to make a significant dent in the percentages. If there were that many, they would've detected them by now. And, if there were that much baryonic matter around, it would completely change the geometry of spacetime and affect everything within it.
25-05-2011, 04:06 PM
I always thought that and My astronomy teacher think it is all non-baryonic which is why I on just passed in that essay. overall still doing well.
There is most probably a lot more baryonic matter out there just the equipment is not sensitive enough above the noise floor.
25-05-2011, 04:07 PM
OK Carl Thanks :thanx:
25-05-2011, 06:28 PM
Craig I think you know the answer.
These mental giants are against it because it leads to the topic of magnetic reconnection which is used to explain a variety of "mainstream ideas" from the high solar corona temperatures to auroras. Since mainstream uses it it must clearly be wrong.
What makes it even more laughable is that magnetic reconnection is a subject of plasma physics which these guys supposedly embrace.
To get around this apparent contradiction they claim that magnetic reconnection was supposedly cooked up by mathematicians in collusion with cosmologists.:rofl::rofl::rofl::rof l::rofl:
25-05-2011, 06:58 PM
As I wrote earlier, Steven, they'll consult their ubermenschen masters Rocky and Bullwinkle for sage advice:):P
25-05-2011, 07:04 PM
Had a quick read of the original paper. I think I understood.
They are quoting about 10^-4 to 10^-6 e per cm^3. The temperature ~10^7 K just reflects the very high velocities of the particles making up the the plasma stream. The x-rays produced by Bremsstrahlung is what they are detecting. I would imagine something like the magnetic heating of the Sun's corona is involved only over vast distances.
Rather than guessing what is between galaxy clusters they have produced real measurements. Hindsight always reveals an answer that was under your nose all the time. It is the skill in knowing where to look and what for.
Good stuff from some so young.
25-05-2011, 07:13 PM
The proportions of baryonic:dark matter are provided by the acoustic oscillations in the CMBR aren't they ?
So, even if more baryonic matter is discovered, the proportions would still be what is shown in the CMBR power density spectrum (?)
Interestingly, if there are more dwarf and spiral galaxies discovered, then there would also be more dark matter required for them to 'do their things'.
So, adding more baryonic matter invariably results in the same ratio of DM to baryonic but just more matter (?). The volume of the universe is so big, the density wouldn't change much either .. so once again, additional baryonic wouldn't impact much.
There are lots of different data sets which lead to the need for dark matter, also. Each of these impose their own constraints on the proportions don't they ? (Just like the CMBR).
25-05-2011, 07:20 PM
I think I might have been originally a bit off track with my interpretation of this plasma. Its moving quickly as you point out, but the density is very low!
I don't know whether this could be interpreted as having near-to-infinite conductance. (Hence my frozen magnetic field comment may be off track??) :question: .. (Happy to be corrected).
25-05-2011, 07:53 PM
Pretty much so. If the baryonic matter did increase substantially enough to show up a marked change in the ratio of DM to OM, we would be getting a different PDS to what's been observed. However, you'd have to add that much baryonic matter you'd be able to walk from here to M31, hopping from planet to planet without striking any vacuum!!!!:):P The funny thing is this...as you mentioned, the more baryonic matter (OM) that is present, the more DM is present to allow the OM to "do it's own thing", so to speak. Interestingly, it's the dwarf galaxies which appear to have higher ratios of DM to OM in their makeup. Considerably more so than in most spiral galaxies. So, if you had an overabundance of dwarf galaxies present in the universe, you're ratio of DM to OM would appear to actually increase. In other words, we may be able to use the ratio of DM to OM and the PDS results to predict how much of the baryonic matter is in the form of dwarf galaxies. That would, therefore, put an upper limit to the ratio of DM to OM, in total, and give some constraint to the theory.
25-05-2011, 08:09 PM
As you mentioned before, there's other qualitative constraints as well eg: the large scale structure.
They're also constrained indirectly by the Supernova data, I think.
.. and lensing as well.
They could also play with the different classes of DM to adjust the whole mix, but these would also be constrained by the same measurement data.
This is why they need more info to pin a few of these things down, eh ?
(Like the AMS, Ice Cube, etc).
We might complain bout the non-intuitiveness of it all, but without more data, it'll always seem weird.
That the CMBR and the Standard Model fit so well and produce the same ratios, is totally amazing !
Which is why, I guess we just have to accept it !
25-05-2011, 08:49 PM
As discussed via PM, if a plasma has infinite conductance then E=0.
A plasma can move parallel to the magnetic field lines. In other words the magnetic lines are frozen in the plasma.
The plasma becomes segmented, each segment constrained to a particular magnetic field line. If the field lines are in opposite directions, a current layer can form between the field lines. This increases the resistance of the plasma between the field lines. This has the effect of "unfreezing" the field lines. The magnetic field lines cross over, the plasma segments mix and your get magnetic reconnection and kinetic energy in the process.
The kinetic energy is directed perpendicular to the converging field lines much like squeezing toothpaste out of the tube cut at both ends.
As you are aware our EU friends seem to think plasma physicists are so dumb that it the requires the wisdom of an electrical engineer to tell them that magnetic reconnection is nothing more than inductance at work. :P:P
Yet those dumb plasma physicists have demonstrated magnetic reconnection in the laboratory.
25-05-2011, 08:51 PM
For now...who knows what the scientists in 100, 500 or 1000 years time will say about it. Considerably more, I should think.
25-05-2011, 08:57 PM
Here is some shocking news for you Carl.
Rocky and Bullwinkle do not want to have anything to do with this crowd.
From their website http://plasmauniverse.info/ is this.
25-05-2011, 09:09 PM
They may deny any connection, but they'll still absorb all the "electrical energy" coming from their adoring fans...when it doesn't appear to conflict with their own agenda:):P
In any case, you couldn't call some of the journal papers I've read coming from this mob as being science. Some of them may have a thin veneer of acceptability to them, but others are down and out bizarre.
Not only that, how do you publish anything critical in the relevant journals of the IEEE, or even have any objective review process with submissions, when the senior editor for that particular section of the IEEE is the one person who is pushing this wheelbarrow...Anthony Peratt.
26-05-2011, 09:31 AM
Thanks for this, Steven.
Very interesting video actually.
They talk about 'anomalous resistivity'
you mention a plasma current layer forming between field lines which produces resistivity. (I can easily visualise what you say is happening).
The whole process is once again, very probably a chaotic one, as the initial conditions would be delicately poised and any perturbations could easily (probably) completely alter the outcome and the observed effect.
I guess the ultimate aim of these guys is to 'control' it, so they can contain the plasma for fusion. In the Sun's corona, I would think pure Chaos would reign.
In the video, when 'Russell Kulsrud' starts drawing it all up on his blackboard, I find it fascinating that he starts by drawing up 'interstellar matter forming in a uniform magnetic field'
that's the crux of the issues with EU .. right there. I have more to say about this .. (I'll leave it to a separate post), but suffice it to say that clearly magnetic reconnection is real enough for these guys to have been granted funding to research it.
I fail to understand why this wouldn't occur. You can almost visually see it happening, when you look a how a flare develops on the Sun.
The EU view on this, I think, is purely motivated by outdated Arpian views, exacerbated by the seeming paucity of research done on all this, since. (Probably because of the difficulty in reaching the temperatures and doing lab measurements ??) ..
This reconnection issue, to me, is an interesting aside to the main issues highlighted by this recent analysis work however. I'm eager to discuss these issues in my next post.
Thanks kindly for the run-down on reconnection, though !
Heaps more to learn up on about this stuff !.
26-05-2011, 09:52 AM
Arpian...yes, but I think you mean Hannes Alfven, Craig. He's the guy that the EU seem to think is God...everyone else is wrong according to them.
26-05-2011, 09:54 AM
Yep .. (oops) .. too much goin' round in my head at the moment !!
Thanks for the correction.
26-05-2011, 10:15 AM
Ok .. so coming back to the original research topic, there are some issues I feel somewhat confronted about. In keeping with my goal of remaining open-minded, I think an adjustment of my thinking about intergalactic fields and currents etc, needs altering in the light of this 'discovery/evidence.
So, here goes:
i) Primordial intergalactic magnetic fields exist. They stretch over huge distances, and are very weak in terms of flux densities;
ii) Plasmas and ionised gases, (in differing states of ionisation), get caught up in these fields. The intersection of one or more of these fields may influence the initial formation of this matter, aggregating it into various 'odd' shapes which may then go on to form galaxies or stars, etc. The simultaneous localised 'clumping' of dark matter, would have to occur once the ionised mass acquires sufficient concentrated mass, and ultimately self-organises into halos. This would happen once the ionised matter itself, acquires sufficient matter density to pull itself into the classical spherical shape, (the hallmark of gravitational attraction).
I can see no reason why electrical, magnetic and gravitational fields wouldn't continue to influence the initial formation stages (and perhaps, subsequent stages), of the baryonic (ionised) 'matter'.
iii) A paper referenced in Amelia Fraser-McKelvie etal's original paper (by Kawahara et al, Jan 2011 (http://arxiv.org/pdf/1101.0614v1)), focuses on observations of a merging group of galaxies at one of these intergalactic filamentary junctions. In the abstract and introduction, they keenly point out:
So, it would seem that they are looking at something of an anomaly, so it would be highly speculative to say that all galaxies are formed at the junction of intergalactic filaments. (Probably easy to disprove such an assertion).
iv) Amelia etal, stated that:
So, it should be noted that if one were to attempt to make an EU type case, one should be looking for evidence of giant intergalactic plasma using these detection methods. (Let's not use the "BC" term … ie: "Birkeland Currents").
My purpose behind this post, is mainly for me to clarify my understanding (as it stands today) of what is actually a reasonably supportable perspective on the likely Astrophysical process for which evidence exists .. without being particularly bound up in 'gravity dogma' (a label which I vigorously dispute), or EU nonsense (a term easily demonstrated).
Corrections/feedback requested, kindly.
PS: I've 'squirted' this one out in a hurry as I notice IIS is about to go offline. I will make corrections if I've blooped anywhere .. later. :)
26-05-2011, 10:17 AM
I've just figured out the hierarchy of the EU Universe and the relationships between the players:):P
1. Primal Source: GOD (Hannes Alfven)
2. Archangels: Rocky and Bullwinkle (Peratt and Lerner)
3. Menial Worker Beings: Dick Dastardly, Muttley and The Gruesome Twosome (Don Scott and Co)
4. The Great Unwashed of Disciples: (Sparky and his mates)
26-05-2011, 10:18 AM
PS: I notice that TBolts, perhaps coincidentally, has commenced a thread which parallels this one. (http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?f=3&t=4642)
It might be interesting to see the differences in views, as both threads proceed.
26-05-2011, 10:23 AM
Their whole thread will be a joke, from start to finish.
Edit: Just read their posts...ignorant idiots.
26-05-2011, 10:26 AM
So lets make a better one !
26-05-2011, 12:00 PM
Instead of putting ourselves in a position to be accused as dismissive and exclusive and orthodox let's be more analytical and disprove EU nonsense by demonstrating WHY and where exactly it is nonsense. This will result in much better reception from people on this forum, that can't make up their minds, for whatever reason.
I tried to use this approach in dealing with some people in the past and while I don't think that this was the only reason why that particular person is absent from this forum, I feel it was highly effective [still no answer to my question "why pulsars (if they are indeed relaxation oscillators) are so precise"].
So... yes, lets make a better thread.
26-05-2011, 12:02 PM
I agree, that's what we should do.
Bojan, you'll never get an answer to that question. They have no way of providing it.
26-05-2011, 12:05 PM
So does anyone agree/disagree with anything I wrote in my post #42 ?
26-05-2011, 12:15 PM
Well.. EM fields will stop to be a factor when ionised plasma recombines (de-ionises).
From this moment, magnetic field is "disconnected" from (baryonic) matter.. and gravity takes over.
IMHO, of course... just gut feeling.
26-05-2011, 12:37 PM
Well, the Sun continues to generate its own EM fields when things heat up. Gravity is doing its thing there also, (clearly). So both must exist simultaneously in that particular process. Gravity may have little/no effect where a plasma is distributed, but in this instance, the plasma might also still be following these primordial fields in deep space environments.
The initial primordial fields could still continue on their merry way, also. I don't think these fields are necessarily caused by moving plasmas but they seem to trap free plasmas. These fields seem to be referred to as: 'always have existed, and will continue to exist' by mainstream papers (??)
Both of the fields mentioned in paras 1 & 2 could be thought of as separate from the EM fields set up in Birkeland currents, which might happen around highly magnetic objects, already possessing intense fields. Which cause acceleration and intense Bremstralung & Synchrotron radiation, (etc), (which could be detected from Earth).
(Just trying to separate the different 'fields' here .. I think what I'm saying may be supported in the mainstream literature I've read so far.
Another thing also, electrostatic forces seem to be cited as playing roles in pulling together dusty aggregates. I can see this assisting the planetary clumping process (before gravity kicks in).
26-05-2011, 12:45 PM
Hmm.. overall plasma electrical charge is nil (since plasma is highly conductive... it actually has negative resistance (higher the current, lover the voltage drop) apart from local variations.
It is different situation if we have already neutral (and charged to some extent) particles.
This charge (re-ionization) may come from radiation from nearby stars perhaps.. but this means all the particles will be of same charge.. so repulsive force will be in action.
26-05-2011, 12:50 PM
Yep to what you say about plasmas.
No - when it comes to planet formation .. I wasn't clear (my fault)
the planetary formation process still involves electrostatic forces (eg: attraction of cold dust to H2O molecules .. or even dust-to-dust attraction), which starts the matter 'clumping' process (before gravity can take hold) .
Strictly speaking though, you're right .. this is really a different topic from plasmas.
26-05-2011, 01:00 PM
That's a given, nothing out of the box.
Yes, but there is a big problem with that. That's the general weakness of those fields plus the actual mechanisms by which a galaxy forms. You have to take into account the formation of the central black hole, the bulge and its relationship with the BH and then you have to account for the spiral arms (if it's a spiral galaxy), the morphologies of ellipticals and the general haphazard formation of irregulars. Galaxy formation is not a simple cloud---collapse---galaxy scenario. There are many factors which determine what type of galaxy is going to form and then you also have the question of what came first, the central BH or the galaxy.
Now, given how weak the intergalactic EM fields are, you have to come up with a convincing mechanism in which fields that weak can clump together and drive the initial stages of galaxy formation. Even if it's just streaming gases into the nodes where filaments meet, you have to work out what rate of gas flow will occur in fields of such low strength. Not only that, given that the gases within these filaments are at high temps and the gravity in any one area of the clumps is weak because of the low density, you'd expect the high velocity of the particles would prevent the gas/plasma from clumping. In which case, no galaxy formation via clumping due to intrinsic EM fields will occur. Something else has to allow the plasma to clump and begin to coalesce. Where, the EM fields may play a part is in magnetic reconnection. The resistance between bilayers due to opposing currents could conceivably slow the flow of plasmas down and initially cool them (radiative heat transfer/induction and/or mixing mechanisms). That would allow the gases/plasma to clump together and then gravity would do the rest. Once those clumps became large enough, the EMF's would play a secondary role to gravity. It would also be where the initial fields of the galaxies came from as well. Plotting the strength and the morphology of those fields may help to give clues as to how each galaxy formed, along with the usual factors such as rate of star formation, initial rotation dynamics, gas composition etc etc.
The dark matter would appear to be unaffected by the EMF's, so clumping of the dark matter is independent of whether there's one there or not. However, the clumping of the DM would effect the clumping of baryonic matter, so you have to devise a mechanism which allows DM to begin clumping. When you look at the Standard Model, you can see that the galaxy, which form the superclusters, also appear to be congregating in response to higher than normal densities of DM...in those spots. In other words, the DM is allowing baryonic matter to clump together to form galaxies and superclusters of galaxies, acting as a gravitational "glue" which holds them together.
Galaxies may just as easily form outside the junctions of filaments as in them, depending on what's happening within the filaments. And that's what appears to be the case. However, given that the highest concentration of mass is at the filament junctions, you would expect a higher, a priori, chance for a galaxy to form at the filament junctions as it would elsewhere. Or, at least, the formation of a supercluster to occur there, if not the galaxies themselves. Once the galaxies form, the increasing mass of the supercluster forming at the node may draw the galaxies in from the filament, where they have formed, to the node where the emerging supercluster resides.
You can't escape from using the BC term:). I would be inherent in the plasmas. However, it ultimately depends on just how dense the plasmas are and whether they are able to carry any current at all. On the scales that we're talking about, and what has been observed, you're talking about plasma densities so small and EM fields so weak that there's barely enough there to detect, let alone drive a current through. Only for the fact that it's on such a large scale, you would never detect them. There's most certainly no BC there simply because the Xray and such that are being given off by these filaments is come from Bremmstrahlung...the electrons are literally neutralising themselves by colliding with the tenuous gases that are there. BC's require free and uninterrupted current flow along the EM lines. Once reconnection occurs or the electrons collide with other particles in the plasma, the current dumps itself and converts into light and heat. It stops flowing...there's no mysterious, undetectable "dark current" occurring. In any case, for a current to flow you need to have two opposite charge polarised ends to a circuit. In the case of an intergalactic sized filament of plasma, those two charged ends would stick out like sore thumbs observationally. They've never been found.
26-05-2011, 02:01 PM
Agreed. But these issues remain, regardless of what may, or may not have, started the process. I think my point is that DM clumping, and all the fundamental forces must play a role during the initial phases. So just because EM forces may/may not have played some role, doesn't mean that gravity is out of the picture. Its a complex process.
(Captain Chaos strikes again ! :) )
Wouldn't the temperatures go up if the resistance increases (more collisions) ? I've imagined (by reading somewhere ?) that the cooling effects you mention do occur, but would kind of be secondary in terms of overall effect ? (Only a minor point here). As I mentioned above, all of this must play some part as it all comes together. The details are still being sorted through in models, I would think.
Yep - this POSSUM project was supposed to be attempting a new EM map of the universe. They've been quiet for almost a year, now. ??
Yep. I wonder why DM ends up as a 'halo' and not a solid 'sphere' (like baryonic matter) ? :question: (It probably does but I haven't seen this idea turn up yet in the DM maps of the '(un)observable' universe) ...
I recall your questioning the shape of the models used in developing the rotation curves. Perhaps as they get onto more complex models, this 'halo' shape might become less popular (perhaps attributable to this) ?
and then they get ejected .. resulting in quantised redshifts with unmatching redshifts associated with the filaments obviously connecting them !! :lol: (Just kidding .. gotta have some fun!).
The CMBR map, and the theory about where the baryonic matter cooled and formed superclusters takes all this back in time too, eh ?. Things may have moved around a bit since then, so a galaxy appearing at the cross-roads of two present-day filaments, isn't really all that exciting when coming from the idea that it all started from the structure in the CMBR patterns.
Yes and hmm .. :question:
I would think BCs must form once the gases start to aggregate around the primordial (intersecting) fields. Collisions will occur and things slow down, heat up, reconnections, charge separation, EM fields containing the plasmas etc.
Prior to them getting up to noticeable strength however, they still emit Bremmstrahlung and X-Rays. If I'm not mistaken this is exactly how they detected them in this study !?!
The paper says:
These were detected by the means I mentioned. I don't think we can say that they don't exist any more. This paper says they have been detected in the ROSAT All-Sky and the 2dFGRS surveys. There is some doubt that some potential candidates may have been discarded from these initial studies (they started out with some 805 candidates originally and this got paired down to a mere 41).
I think Amelia et al, are suggesting that some may have been overlooked because of discards (due to smaller box sizes) used in the earlier analysis techniques).
26-05-2011, 02:26 PM
Remember, Craig, all the good stuff they've detected occurs when the BC's breakdown because of reconnection and neutralisation of the the ionic plasmas. The BC's would only exist so long as the plasma remained ionised and a free path exists for the electrons/charge to flow, otherwise it just becomes a super thin cloud of hot neutral gas.
26-05-2011, 02:37 PM
In any case, it's not even really "missing mass". It's more a case of overlooked mass that wasn't considered beforehand because they didn't really look for it...or their sampling analysis techniques weren't able to resolve the mass.
You could tell from the way the wallies over at TB waffled on about "missing mass" and "only gravity" that they not only didn't understand what the paper was on about, but also that they hadn't a clue about the science in the first place. Show's you what happens when a mob of "armchair experts" thinks it knows what it's talking about. Even the armchair they're sitting in is riddled with termites:):P
26-05-2011, 04:33 PM
I can't see what you're saying here Carl.
They went out looking for what they call the Warm-Hot Intergalactic Medium (WHIM). This was theoretically predicted to exist, and there has been a lot of theoretical development done in order to select very specific detection technologies at certain redshifts and temperatures. At the higher temperatures, clearly this 'baryonic' matter (ie: gas) is ionised and may as well be referred to as 'plasma'.
Some of the papers I've read on the spectroscopic side, I do not understand. But I can see that they've considered many different mixes of ionised plasma and neutral gases before looking for these filaments.
I am not yet able to understand the fundamental differences between plasmas in a Birkeland Current, and one of these filaments (which they've now detected). I'm not sure there are any differences.
I guess it all comes down to one's definition of the plasma-at-hand and the generalised term 'Birkeland Current' plasma.
It begins to look like this may be where some of the confusion lies.
Until someone can tell me where I've gone astray, I still maintain that Amelia et al, have detected intergalactic filaments which could also be referred to as, (unfortunately), 'giant intergalactic Birkeland Currents', and they appear to persist for very long periods of time.
26-05-2011, 04:46 PM
I found a great paper (http://arxiv.org/pdf/0706.1787v1) which goes into the detection methods for low redshift Baryons. In the abstract, it says:
I have a feeling this defines the term 'missing'. In a nutshell, it was predicted, but not found. It was thus 'missing'. Amelia et al are on the path of finding it.
I'm not sure I understand fully what the paper is on about yet
and I'm only an 'armchair amateur' ! Its very complicated because of the need for a detailed knowledge of the spectroscopic side of it.
26-05-2011, 05:25 PM
A BC needs to have free electrons and a free path i.e. no interference by other particles, for the current to flow. They (the electrons) can be masked by acting as a cloud around the other particles but the moment any of the electrons collide with the particles in the plasma, that's it. The plasma becomes a neutral gas (or only partially ionised). The current breaks down and the collisions generate bremmstrahlung and whatever else.
The plasmas in a BC are fully ionised and the free electrons can either travel masked or free of the other particles....basically, just like battery, the charges separate and the electrical current flow, when it occurs, happens in the same way as occurs in a battery. The masked version is basically what they call the dark current (http://en.wikipedia.org/wiki/Dark_current_%28physics%29). When the EM field sweeps through the plasma and the separation of charge in the atoms of the gas occurs, it basically acts much like what happens in photodiodes or CCD's (which are a type of photodiode anyway) where random electrons are generated as well as holes left over from their generation. Charges moves as one electron fills the hole left vacated by the electron that was removed by the field. It's a cascade effect, if you will. In the case of BC, fully ionising the plasma creates two poles of differing polarities and charge flows between those poles, or from the charge to the neutral ground (in Earth's case, the upper atmosphere). When they travel in a masked fashion, the velocity vectors of both the electrons and the rest of the plasma is the same, so there is no net movement between them. Once the velocity vector of either changes, the particles collide and the charge breaks down, the plasma neutralises and you get the accompanying radiation being given off.
What we have in these filaments is a super thin partially ionised hot gas. It's so thin that the electrons rarely encounter other particles in their immediate vicinity. However, over the distances that are seen in these filaments, the plasmas virtually become opaque to the electrons, so their chances of colliding with another particle becomes quite high. Whilst they can move around at high speed, hence the temperature of the plasma being high, they can't go on indefinitely without colliding with another particle. Hence, over the distances that the filaments cover, there is little or no separation of charge to effect any current flow, despite the filament being mainly a hot plasma and/or neutral gas. The electrons collide within the filament with the rest of the particles and give off Xrays etc.
The plasmas are so thinly spread, in fact, they might as well not even be there. They make the thinnest plasmas we can produce here in labs look like solid lead. When you read values like 10^-4 to 10^-7 electrons per cubic metre, that equates to about 1 electron every 10-100 cubic kilometres or even less. Can't generate too many amps in a conductor that sparse of charges:):P Even on an intergalactic scale.
26-05-2011, 05:33 PM
It's the same as saying overlooked. It wasn't literally missing and not, therefore, a part of what was there. They can find it, however, they need to change their methods to do so, or look at old data with different and new "eyes". That's what Amelia did and she found the "missing" mass.
Truly missing mass would equate to what we call DM. You can barely detect it (and then only because of its gravity) and it just doesn't interact with anything ordinary. You can't see it or detect it in any ordinary sense of the definition. So, it becomes literally missing...nowhere to be seen but it's there because everything else is doing this or that because of its presence.
26-05-2011, 06:12 PM
Thanks for your post #60.
Other than involving theoretical explanations, I still don't see how they can differentiate spectroscopically, between ionised gas filaments detected at X-ray wavelengths via thermal bremmstrahlung emissions (smooth continuous spectrum)
. and an ionised plasma in a BC (smooth, continuous spectrum).
They mention they can also look at observations at 0.65 keV O line in absorption or emission, but these may also appear in a BC plasma (?)
The difference between the two is the charge separation, but how can this be remotely differentiated from an ionised plasma, if the plasma isn't emitting any other EM radiation at different wavelengths ?
26-05-2011, 06:51 PM
The wavelength of the emitted radiation is an indicator of the mechanisms which produce it. BC's produce visible light and radio noise only because they don't have any electrons which are relativistic in nature. Xrays produced via thermal bremmstrahlung need relativistic electrons to be produced. Anything with gamma radiation needs relativistic electrons (or other relativistic particles, e.g. photons) in this situation (ionised plasmas) to be produced. They'll also produce light and radio waves as well. Same with synchrotron radiation....electrons spiraling in a magnetic field and accelerated to relativistic velocities. Basically a Bennett Pinch and not a BC.
27-05-2011, 11:24 AM
After much reading, I think I'm now getting a much better understanding of how all this fits together
The Big Bang/Lambda CDM Theory says that following the Reionisation Epoch (near z~6), (by which time, most of the intergalactic medium had been photoionised to a temperature of about 10^4K), the predominant heating mechanism was through thermal shocks that developed as large-scale density waves collapsed in the dark matter. This pushed the temperature up to the 10^5K region in the volume for z<1. Systems and galaxies develop with temperatures of 10^7 to 10^8K, which can be observed by X-Ray telescopes.
So, what was predicted by the Big Bang/Lambda CDM model, was that these 'WHIM' filaments may be detected at X-ray wavelengths at a volume of z<1, and would be produced by thermal bremmstrahlung emission.
So what they've now observed is:
- soft X-Ray emissions in two energy bands: 0.9-1.3 keV and 0.5-2.0 keV. ('Soft' X-Ray emission is from about 0.12 keV to 12 keV).
- the thermal temperature range predicted by theory, translates to 0.0086-0.86 keV (10^5 to 10^7 K), so what they've detected falls (somehwhat) within these bands.
The thermal bremmstrahlung radiation is given off by electrons, as they are scattered by the strong electric field near the other high speed nuclei (ionised) in the filaments. These X-rays have a continuous spectrum. So, this is the source of the X-Ray emissions.
Now, I personally think that the term 'Birkeland currents' is hugely generalised and not particulary well-defined. The spectral emission energies in Earth's Auroras, can range anywhere from 1 to 200 keV, which still overlaps with what Amelia et al have detected. (As avery rough example of a well-known Birkeland Current phenomenon).
As such, it appears that the only reasons I can find, to rule out that what Amelia et al have observed may be a 'Birkeland Current', is a well-defined, empircally plausible, cause mechanism (ie: some evidence of a huge, self-sustaining intergalactic battery at either end of the filaments, to create the initial current flow in the filament). The self-sustaining mechanism which ensues, requires charge separation to be maintained continuously in the filament and it is a complete mystery as to how this can happen, unless energy is continuously added to the filament. If reconnection conditions occur, energy would be lost, and distinctive emissions would be able to be detected. So where could this big-battery possibly come from ? .. all sorts of story-telling then ensues, with little/no specific observational evidence, for the case in hand .. ie: for example, take the filament from Abell 2829 to Abell 0118 .. ~ 20 Mpc in length ? Are Abell 2829 and Abell 0118 somehow able to act together as a giant anode/cathode pair ?
The BB/Lambda CDM model on the other hand, defines a cause mechanism and made the prediction, and Amelia et al found the smokin' gun !
That's my take on it all.
Has anyone ever seen any papers which classify the spectra of Birkeland Currents having typical space-bound plasma environments ? (This information may help to differentiate a BC from an ionic gas plasma filament, at least spectroscopically).
27-05-2011, 12:26 PM
Craig...don't give the EU guys a smell of the oily rag, mate:):P
They'll jump at those suggestions and run with them like they're pots of gold at the end of the EU rainbow:):P
They'll start looking for the giant "Energiser" AA cells in space, next:P
Or the Energiser Bunny (although they probably see him anyway:):P)
I haven't seen any papers offhand, but I would imagine there are some.
However, if you have some sort of "battery in space", it's like I said in a previous post....it's going to be very obvious observationally. You would have to have a +ve and -ve charge end to the filaments and that's not what is seen. Not only that, the polarities would have to be self sustaining over enormous periods of time and you have to invoke a mechanism that can enact that charge separation. I can't think of anything astrophysical that could do that. Not anything that immediately comes to mind.
27-05-2011, 12:53 PM
Is this supposed to be a absorption/emission line for a BC?
If you can confirm this then it is may be possible to differentiate between a plasma (or a gas with a low ionization content) and a BC.
A BC current is a magnetic field aligned current hence it is possible for the emission/absorption line in the spectrum to split in the presence of the magnetic field.
This of course assumes the plasma or low ionization gas is not in an external magnetic field.
27-05-2011, 01:52 PM
Unfortunately, my wording was an artifact from my grappling/questioning whether a BC and the filaments observed may be detected using similar means.
The 0.65 keV absorption/emission referred to in Amelia's paper, was alluding to one of the means her predecessors have attempted to use to detect these filaments.
Whilst exploring in the UV region, they have previously attempted to use OVI and HI Ly alpha lines as a possible probe of gases in the near to 3x10^5 K temperature region. Beyond 3x10^5K, these lines are of little use, and X-Ray lines become more important. Apparently, due to the absorption by neutral gas in the Milky Way, there is a natural divide between the UV and X-Ray regions. The UV region ends at 13.6eV and the X-Ray region becomes more useful above 200 eV.
Hydrogenic oxygen (OVIII), absorption, has an equivalent Ly alpha line at 654 ev. I think this is what Amelia was referring to.
I found a great paper on all this (http://arxiv.org/abs/0706.1787) (from where the above info is sourced).
Page #5: "Section 3: Atomic Physics", talks about the 'ins and outs' of the physics side of it.
It'd be great if you could have a squizz at it.
I'd like to take a punt, and say that if these lines appeared in the spectrum of any filament, and were found to be split, courtesy of the Zeeman effect, then that could be used to infer a Strong Magnetic Field
presto .. there's ya BC!
If not, why not ?
Great idea !
27-05-2011, 04:57 PM
This conversation is way over my head but I thought youse might like this.
29-05-2011, 11:12 AM
There appears to be quite a few other ways these guys have developed to detect these ultra-thin (density-wise) filaments, all having their strengths and weaknesses:
- X-Ray and UV absorption lines (primary tool);
- X-Ray emission (inside and near Galaxy Clusters .. note!);
- soft excess emission within the virial radius of galaxy clusters;
- the absence of OVI emission;
- OVII and OVIII emission;
- looking for shadows in the X-Ray spectrum caused by X-Ray opaque clouds against a background emission by a filament;
- dispersion: (ionized plasma has a frequency-dependent index of refraction, which produces a measurable effect at radio wavelengths) - Interesting !!
- radio 'hyperfine' lines and;
- the Sunyaev-Zeldovich Effect.
So, at the end of the day, interstellar ionised gas filaments CAN be detected and it appears that 41 bona-fide inter-cluster filaments have been detected and catalogued to date.
It may be possible to distinguish (spectroscopically) a 'filament' from a hypothesised inter-cluster 'Birkeland Current' (BC), depending on its energy level, (ie: its state of excitement/state of discharge). This would be (perhaps) done, depending on the strength of its magnetic field, via the Zeeman Effect ... although, this is subject to other possible causes, which would have to be ruled out by other evidence/arguments.
The X-Ray emission mechanism from the filaments detected, is stated by Amelia's paper, as being caused by thermal bremsstrahlung radiation. This is also what would be, (presumably), expected to emitted by a BC in the latter stages of 'dark mode', probably in 'glow mode' and surely in 'arc' mode (a synchrotron radiation spectrum would also be expected in 'arc' mode (??)).
That about sums it up for me. None of the (lots) of papers I've read on this mention anything about the filaments being current-carrying BCs (not surprisingly, I suppose). ;)
There is much discussion about whether the gas filaments are infalling/ejected from the clusters themselves. The cause of the filament X-Rays, seems to have a plausible explanation in the BB/Lambda CDM Standard Cosmological Theory sequence (post re-ionisation epoch at redshift ~6), where shock mechanisms imparted the thermal energies needed for X-Ray emission (at redshifts < 1).
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