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Giant Galactic Blobs!

  1. Jan 11, 2005 #1

    Garth

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    What are Giant Galactic Blobs?

    Perhaps these will give a clue as to the nature of galactic haloes and the inter-galactic medium, and perhaps identify Dark Matter as well?

    Garth
     
    Last edited: Jan 11, 2005
  2. jcsd
  3. Jan 11, 2005 #2

    ohwilleke

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    This seems to be a bad link.
     
  4. Jan 11, 2005 #3
    I doubt it will identify dark matter. It seems the blobs are primarily made up of hydrogen. We already know that the inter-galactic medium in clusters of galaxies is enriched (to about 1/3rd of the solar abundance of heavier elements) by galaxies via some mechanism (eg. ram pressure stripping, supernova explosions etc), however it is generally thought that the hydrogen in the inter galaxy medium is primordial.

    If you look at the links to the pictures they had, there was a small blurb that mentioned a fairly plausible idea (in my mind!) that the blobs origionate due to supernova explosions of massive star that are produced during an intense star burst, triggered by the merging event. These explosions create a 'superwind' which shoot gas outwards. here's the link:

    http://www.spitzer.caltech.edu/Media/releases/ssc2005-03/ssc2005-03b.shtml

    Matt
     
  5. Jan 11, 2005 #4

    Garth

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    Thank you I have fixed the original link now - it is slightly different to yours Matt.

    The question is do the blobs originate from the galaxies and are expelled from them, or is the blob 'primordial' and perhaps the remnant of the galaxy forming process?

    If so are they still there around our Local Group, perhaps in some evolved form ? and actually the DM component is baryonic in nature?

    Garth
     
  6. Jan 11, 2005 #5
    I don't know whether the blob is a remnant of galaxy formation. If it were, blobs would be seen around other galaxies which are not merging. From what I read in the link, it seems the blobs occur in merging galaxies, hence are probably not primordial.
     
  7. Jan 11, 2005 #6

    Nereid

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    Speaking of primordial ... dwarf galaxies are sometimes thought of as being 'unevolved remnants' ... this recent Subaru result suggests that at least one (Local Group) dwarf is anything but 'pristine'.

    Speaking of strange, local denizens, does any PF member have comments about these dwarf compact objects in the Fornax cluster? Ditto, these 'faint fuzzies'?

    (note to turbo-1: they do not have discordant redshifts, are not quasars, and don't seem to be 'near' Seyferts).
     
  8. Jan 12, 2005 #7

    Chronos

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    I just don't see dark matter going away anytime soon. BBN, for one, still harshly constrains how much missing matter can be baryonic. For a fairly recent paper see:

    Big Bang Nucleosynthesis
    http://arxiv.org/abs/astro-ph/0406663
     
  9. Jan 12, 2005 #8

    Garth

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    Chronos -Yes but let the observations drive the theory and not the other way round!

    We have evidence of the gravitational pull of DM but conclude that it cannot be baryonic because theory says so.

    On the other hand we are observing hot gas, "giant galactic blobs", Lyman alpha forests etc. etc. all of which are baryonic; not to mention the possibility of not-yet-observed evolved, i.e. condensed, baryonic matter in such forms as black holes, 'Jupiters' and 'bricks', to mention a few.

    If we add the masses of all these components, together with luminous material i.e. galaxies, we may find the overall baryonic density stretches the standard BB 4% limit.

    Solution? If (a big 'if') the theory does not fit the observation - then modify the theory!
    My suggestion would be to consider the 'freely coasting' scenario more seriously.

    Garth
     
    Last edited: Jan 12, 2005
  10. Jan 12, 2005 #9
    there would have to be an absolute crapload of unobserved baryons to make up for DM!

    Think of a cluster of galaxies. Observed (ie. luminous stuff) mass makes up around 20% of the total cluster mass (90% of which is the x-ray emitting intra cluster medium) . DM accounts for around 80% (roughly). A typical clusters has a mass of ~[tex] 10^{15} M_{\odot}[/tex]. So there has to be lots of extra (unobserved) baryons to account for!

    Matt.
     
  11. Jan 13, 2005 #10

    Garth

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    May it be that the 'Giant Galactic Blobs' are a new observation of part of these "unobserved baryons"?

    We also have to account for the deep vacuum of the intergalactic voids, which cannot be explained by the standard model, because there has not been enough time for matter to differentiate in density under gravitational attraction. Perhaps the voids are not such a deep vaccum after all but filled with diffuse and dim unobservable ordinary matter?

    Within a galaxy or galactic cluster there may be a MOND type modification to gravitation that explains the missing mass.

    I think we would do well to keep an open mind.

    Garth
     
  12. Jan 13, 2005 #11

    Chronos

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    There is a great deal of unobserved baryonic matter - in fact, too much. I don't think this is a case of theory driving observation, quite the contrary. When you look at the observed distribution of matter and the observed motion of matter on large scales, it is hugely inconsistent [far beyond the error bars] with theory. Clearly one or the other must be incomplete. WMAP was pivotal in deciding the issue. By confirming the topology of the universe is truly indistinguishable from one that is perfectly flat, the most reasonable conclusion is we have not seen the vast majority of gravitating matter in the universe. I think it's an even bigger mistake to force theory to fit observation when observations do not conclusively rule out theory. Especially when theory is so fundamentally sound mathematically and internally consistent across multiple disciplines. Adding enough unseen matter to gravitationally balance the books is not a rash step. At this point, all the evidence suggests the majority of this unseen matter does not behave like ordinary matter aside from gravitational effects. Theory provides possible descriptions of the nature of such matter. It also predicts detection is difficult given current methods and technology. It seems reasonable to allow for the possibility theory is sound and give the observation side a chance to catch up. Theories that have otherwise proven sound should not be abandoned until thoroughly discredited by observation.
     
  13. Jan 13, 2005 #12

    Nereid

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    Something I've been meaning to do since at least when Garth first posted SCC ... find a recent, good review paper on observational constraints on DM. You know,

    1) here's how much DM there is in the solar neighbourhood, inside ~35 kpc in the MW, out to the MW halo, within the LG, near the LMC and SMC, near M31, near M33, near the LG dwarfs, within other nearby groups (e.g. M81), within nearby clusters (e.g. Virgo, Fornax), near the large and small galaxies in these clusters, within nearby superclusters, ... and how it is distributed

    2) here are the techniques used to make these estimates, along with errors, systematics, and strengths and weaknesses (oh, and theory dependence)

    3) here is a summary of the analyses which conclude that the DM in {x} has a non-baryonic component (and estimates - ranges - of what that is)

    4) here are some attempts to 'make the DM go away', their domains of applicability, successes and failures, etc

    While showing that within the mainstream there is some nice consistency between the 'local' and the cosmological, I feel it's also important to note that what leads to 'DM' conclusions varies a lot, depending on 'what' and 'where' e.g. no matter what cosmological model you choose, there's lots of 'local' DM, and at least a significant fraction of at least some of the local DM must be non-baryonic ... unless you tweak GR (e.g. a la Bekenstein).
     
  14. Jan 13, 2005 #13
    We should keep in mind that dark matter is also important in the formation of large-scale structure. As many people know, there are two competing theories for the formation of structure: the Top-down scenario and the Bottom-Up Scenario. Theorists actually prefer the second: galaxies are formed of little building blocks, then galaxies form clusters, then superclusters. One of the characteristics of a universe filled with cold dark matter is that the universe develops the Bottom-up scenario... I'm not sure if this would be true with a universe filled with baryonic Dark matter...
     
  15. Jan 13, 2005 #14

    Garth

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    meteorGravitationally there's no difference between baryonic and non-baryonic DM, there's just more ordinary 'stuff' to make galaxies out of if DM is baryonic.

    BTW Nereid SCC is also a tweak of GR a la Bekenstein, except it only adds a scalar field rather than scalar, vector and tensor fields. A case for Ockham's razor?

    Garth
     
    Last edited: Jan 13, 2005
  16. Jan 15, 2005 #15

    Nereid

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    Er, no.

    The key difference (at least so far as I've checked things out) is that Bekenstein manages to make the ugliness of the mainstream accounting for (spiral) galaxy rotations curves (and various stuff about dwarf systems too, possibly) ... by encompassing MOND in one fell swoop. AND he also manages to overcome two of MOND's biggest (consistency with good observations) weaknesses - gravitational lensing and cluster 'DM'.

    I've been pressing you (maybe not hard enough) from Day1 to show that SCC makes the spiral rotation curves problem 'go away' (i.e. without 'awkward' DM profiles), AND account for the many excellent, independent observations which lead to the conclusion that there's an awful lot of 'DM' in (local) galaxy clusters.

    To put it crudely, as I did earlier today wrt those who feel 'local realism' is all we need (QM? bah, 'real men' don't need that!), I'll walk out on my 'marriage with the mainstream' in a heart-beat; just show me the consistency!
     
  17. Jan 16, 2005 #16

    Garth

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    Thank you Nereid that is a good point and it is 'work still in progress'.

    SCC in the first instance does not make "the spiral rotation curves problem 'go away'" and is in the same position with them as the standard model. The difference being SCC identifies any DM required as baryonic. (The problem for SCC is to explain why it is not observed, which is why the Giant Galactic Blobs may be significant)

    However, as an educated guess, this role of 'baryonic DM' may only hold for the cosmological DM, in order to make the matter density parameter up to 0.22 from 0.04, but not for individual galaxy rotation profiles.

    The reason being that a static spherically symmetric solution of the SCC field equations has yet to be found for an extended density such as a galaxy rather than a condensed central mass such as a star. Even in that case the SCC gravitational acceleration in the Jordan frame is modified Newton:

    d2r/dt2 = -[1 - GM/(rc2) + ...]GM/r 2

    but this does not give the MOND acceleration equation.

    One intriguing thing about MOND is that although it does not explain cluster dynamics i.e. 'cluster DM', or 'cosmological DM' yet it may be connected with dynamics on a cosmological scale. The MOND anomalous acceleration a0 = 10-8cm.sec-2 is roughly equal to the Hubble acceleration cH, which is the clock drift in SCC between 'atomic' and 'gravitational' (ephemeris) time.

    Garth
     
  18. Jan 17, 2005 #17

    Chronos

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    Garth, I respect what you have done, but I think it is wrong. The orbital decay in binary pulsars is a stake in the heart of the Jordan reference frame. I really did not understand how SCC explains this.
     
    Last edited: Jan 17, 2005
  19. Jan 17, 2005 #18
    what is this SCC?
     
  20. Jan 17, 2005 #19

    Garth

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    matt.o SCC = A New Self Creation Cosmology.

    Chronos Thank you, any gravitational theory must be vulnerable to falsification by experiment and observation, as indeed is GR.

    The orbital decay of binary pulsars is a good case in point and is dealt with in my paper A New Self Creation Cosmology. The SCC prediction for such is the same as GR.

    This is because the basis of the theory is GR - BD (Brans Dicke) modified by allowing the BD scalar field to interact with particles, as well as perturbing space-time. It interacts according to the 'Principle of Mutual Interaction' (PMI) in which: "The scalar field is a source for the matter-energy field if and only if the matter-energy field is a source for the scalar field."

    Degenerate matter, such as in the Pulsar's neutron star, is highly relativistic. Its equation of state is traceless, as is that of a photon gas, and like radiation it is de-coupled from the scalar field. The matter-energy field no longer is a source for the scalar field and therefore, by the PMI, the scalar field is decoupled from a neutron star. Hence the scalar field does not interfere with the binary pulsars’ orbits. According to SCC their orbits revert to the equivalent GR orbits and consequentially orbital decay from gravitational radiation is the same in both cases.

    What is different between the theories is the collapse of the progenitor stars, when they become degenerate in the first place.

    In SCC G is 3/2 the measured Newtonian G, although this increased gravitational attractive force is compensated by an opposite scalar field force. However, as the stars become degenerate this latter force fades away when the scalar field decouples. Consequently the gravitational force increases to its 'naked' value and the system behaves exactly as an equivalent GR system except the forces involved are 3/2 the normal value. Consequently, using Kepler to evaluate the masses of each star results in values 3/2 too large. Also, the sudden apparent increase in gravitation would cause circular orbits to become elliptical. Therefore the observation of any pulsars with more or less circular orbits around their companions would be difficult to explain in this theory.

    Furthermore, during stellar core collapse to the white dwarf stage the scalar field would gradually decouple, and the gravitational force increase to its 'naked' value, thus encouraging further collapse. Hence I conclude the Chandrasekhar limit is only 2/3 of its standard value of 1.4 MSun, that is only 0.93MSun.

    So if our Sun did not lose too much mass in its red giant phase it too could become degenerate. Whether this is a feasible conclusion or not I leave up to you.

    Garth
     
    Last edited: Jan 17, 2005
  21. Jan 17, 2005 #20

    Chronos

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    That results is some pretty weird gravity effects during the collapsing phase. And that is not to say it is wrong. Neutrinos were basically invented to bridge the 'missing energy' gap in supernova under current theory. How does this work in a Jordan reference frame? I perceive that under SCC energy conservancy only works globally in a BD scalar field, but, how does that solution differ from GR? Furthermore, shouldn't local effects [SR solutions] should be far more obvious than is evident?
     
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