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Existence of dark matter questioned

  1. Feb 14, 2004 #1

    wolram

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    http://physicsweb.org/article/news/8/2/4

    6 February 2004

    Many astronomers believe that the universe is dominated by cold 'dark matter' and 'dark energy' - a view that has been confirmed by recent measurements on the cosmic background radiation. Now, however, a group of astrophysicists in the UK has found that this radiation - the microwave 'echo' of the big bang - may in fact have been modified or 'corrupted' as it passed through galaxy clusters on its way to Earth. The result could undermine previous evidence for both dark matter and energy (Monthly Notices of the Royal Astronomical Society

    http://arxiv.org/abs/astro-ph/0306180
     
    Last edited: Feb 14, 2004
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  3. Feb 15, 2004 #2

    wolram

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    http://www.astronomy.com/Content/Dynamic/Articles/000/000/001/287mlhdf.asp [Broken]

    Ninety percent of the universe and the majority of mass in galaxies are accused of being made of a mysterious and unseen material known as dark matter. But a team of astronomers from Australia, Italy, the Netherlands, and the United Kingdom have undertaken the first search for dark matter in elliptical galaxies and come up empty-handed.
     
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  4. Feb 15, 2004 #3

    marcus

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    a preprint that goes with this article in "Astronomy"
    is
    http://arxiv.org./abs/astro-ph/0310874

    it is by Michael Merrifield and Aaron Romanowsky, two of those quoted by the "Astronomy" report.

    ----------
    wolram, how much bother would it be for you to collect all the links
    challenging the dark matter hypothesis into this one thread?
    Have you got so many that it would be too much work?
    If so you could be selective and just put the links to the most recent, or to what you find the most convincing.
    -------------

    Nereid has a bunch of evidence (links) supporting dark matter. One could kind of line it up and compare.

    this merrifield/romanowsky article (from U. Nottingham I think) is
    straightforward enough---they found planetary nebulas around ellipticals moving slower, the further out they were.

    it is already pretty good to be able to see the out-lying blobs like gnats around the Big Mother Elliptical
    and they used a special new device that not only can
    discern the blobs but apparently can estimate how fast they are moving. a new "planetary nebula" spectroscope.

    this doesnt stop the argument but it does score points

    what else do you have?
     
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  5. Feb 15, 2004 #4

    wolram

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    Astron. Nachr./AN 32X (200X) X, XXX–XXX
    arXiv:astro-ph/0311607 v1 27 Nov 2003
    Toward a detailed view on the kinematics of intermediate
    luminosity early-type galaxies no dark matter candidates
    G. COVONE1 AND N. R. NAPOLITANO2
    1
    Laboratoire d’Astrophysique de Marseille, traverse du Siphon, 13012 Marseille, France
    2
    Kapteyn Astronomical Institute, Landeleven 12, Post Office Box 800, 9700 AV Groningen, the Netherlands
    Received date will be inserted by the editor; accepted date will be inserted by the editor
    Abstract. In several nearby L  L* early-type galaxies, recent observations at large radii have shown a indications of a lack
    of dark matter, substantially at odds with the prediction from the Cold Dark Matter (CDM) hierarchical merger models. Here
    we discuss a pilot observational project for the study of the internal kinematical and dynamical properties of this remarkable
    sample of galaxies.
     
  6. Feb 15, 2004 #5

    wolram

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    marcus.
    the evidence for dark matter vastly outweighs the
    evidence for no dark matter to date, i will use only
    the papers from "respected" sources and post them.
     
  7. Feb 15, 2004 #6

    marcus

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    I wish we had Nereid's advice on this.
    it seems like a good thing to do (to me)
    unless there are so many articles that it would be
    a lot of bother for you to list them.
    but I am curious as to what she would say.

    I know your sources are legitimate scientist
    sources---that's what I am used to seeing from you---
    and they do make the most credible evidence (even if the other
    ones can occasionally be right too)----so that is not the
    issue
     
  8. Feb 15, 2004 #7

    wolram

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    arXiv: astro-ph / 0309823 30 Sep 2003
    Errors in equations for galaxy rotation speeds
    Kenneth F Nicholson, Caltech Alumni
    knchlsn@alumni.caltech.edu
    nd364m@aol.com
    Abstract
    Shown are the errors and difficulties of the equations used for galaxy rotation speeds in the book
    "Galactic Dynamics" (Binney and Tremaine). A usable and accurate set of equations is then presented.
    The new equations allow easy determination of galaxy mass distribution from the rotation profile with no
    need for dark matter or any knowledge of galaxy surface light.
    -------------------------------------------------------------------
    i can not comment on this on, maybe you math people
    can?
     
  9. Feb 15, 2004 #8

    wolram

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    http://star.arm.ac.uk/nam2003/Press/press_nam18.html [Broken]

    An international team of astronomers has discovered that "dark matter", the mysterious material that seems to make up most of the mass of galaxies, is not as all-pervasive as previously believed. Surprising new results from studies of several elliptical galaxies show they are not surrounded by halos of dark matter as was expected. The findings will be presented at the UK/Ireland National Astronomy Meeting in Dublin on Wednesday April 9th by Dr Aaron Romanowsky of the University of Nottingham.
     
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  10. Feb 15, 2004 #9

    wolram

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  11. Feb 15, 2004 #10

    wolram

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    as you say marcus, on the surface its six of one and
    half a dozen of the other, but dark matter and
    dark energy opened up a hole new area for research,
    lots more to wright about and mysterious to boot.
     
  12. Feb 16, 2004 #11
    There has been a lot of speculation about Dark Matter/Dark Halo's over the past number of Years.

    The usual Hubble Classification of Galaxies (I may be incorrect, long time since I read up on it), but I think it goes like this:

    Elliptical Galaxies >E0-E3-E7 for instance? The first order of E0 are highly Spherical(not flat) and have a High luminosity rating, and therefore the Dark Matter is based on Galaxies being squeezed/flattened by the lack of Light(luminosity) as a Galaxy grows old/ages, the Luminosity of a Galaxy becomes 'DARK' over time.

    I remember sending NASA 'ask an astronomer' a question based on my observation that all E0 galaxies were not flattened by the Space that surrounds them, and was inquiring to if there was a LUMINOSITY correlation to the existence of Dark Matter and Luminosity, Highly luminous Galaxies have a lot of Photons pouring out from them, so they have a lot of WHITE-BRIGHT-MATTER emminating around them.

    There reponse I got was:Thats interesting!..nobody had asked that question before?

    As galaxies aged they become Spiral and Barred out, they also become flat as the 'Darkness' increases because of the Luminosity diminishing, they in effect get Squashed more by the Vaccum of Space(a highly luminous Galaxy produces opposing pressure to collapse).

    This of course is based on a number of other paramiters and is my personal take on Dark Matter/Energy Evolution.
     
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  13. Feb 16, 2004 #12

    wolram

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    http://arxiv.org/PS_cache/astro-ph/pdf/0212/0212552.pdf [Broken]

    how to measure real real space (as opposed to redshift space)power.
    --------------------------------------------------------------------
     
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  14. Feb 16, 2004 #13

    wolram

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    ranyart.

    There reponse I got was:Thats interesting!..nobody had asked that question before?
    -------------------------------------------------------------------
    an amazing admission from nasa
     
  15. Feb 16, 2004 #14

    wolram

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    http://arxiv.org/abs/astro-ph/9407019

    We re-examine the systematic errors in the determination of the primordial helium abundance, $Y_{\rm P}$. We find that the systematics are significantly larger than the statistical errors. The uncertainty in (the determination of) $Y_{\rm P}$, is thus, larger than is currently claimed. Furthermore, most of the systematics lead to underestimate of $Y_{\rm P}$. The new upper bound allows cosmological models with no non-baryonic dark matter in which $\Omega_{baryons} = \Omega_{BBN} = \Omega_{dyn}$.
     
  16. Feb 16, 2004 #15

    wolram

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    http://www.aeiveos.com/~bradbury/Astronomy/MOND.html

    A modification to the standard model of Newtonian Dynamics has been proposed to resolve the problem of the missing Dark Matter.
    ----------------------------------------------------------------------------
    http://nedwww.ipac.caltech.edu/level5/Ashman2/Ashman4_3.html
    Throughout this Section it has been assumed that stellar velocity dispersions reflect the gravitational potential of a system in virial equilibrium, so that velocities exceeding those that can be explained by the visible mass in dwarf spheroidals are interpreted as evidence for DM. There are two possible ways of avoiding this conclusion that have been discussed in the literature. The first is the suggestion by Milgrom (1983) and others that at low accelerations Newtonian gravity breaks down. Since this suggestion has implications for all types of galaxies I defer a discussion until Section 11.
     
  17. Feb 16, 2004 #16

    wolram

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    http://www.gsfc.nasa.gov/topstory/2004/0107filament.html [Broken]

    "To explain our results," said Francis, "the dark matter clouds that lie in strings must have formed galaxies, while the dark matter clouds elsewhere have not done so. We've no idea why this happened - it's not what the models predict."
     
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  18. Feb 16, 2004 #17

    wolram

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    http://physicsweb.org/article/news/04/10/3

    Two years ago, the Boomerang experiment photographed with unprecedented accuracy fluctuations in the temperature of the microwave background - the radiation left over from the big bang - in a patch of sky at the South pole. As expected, the results revealed a peak consistent with a 'flat' universe that has just enough energy to continue expanding forever. As expected the Boomerang team also detected a second peak, but it was considerably smaller than predicted. A possible explanation of this finding is that there might be twice as much baryonic material in the universe as has been detected so far, and that it could be hidden inside galaxies.
     
  19. Feb 16, 2004 #18

    wolram

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    http://arxiv.org/abs/astro-ph/0401398

    Newtonian mechanics indicates that galaxies and galaxy clusters are much more massive than we would have guessed from their luminosities, with the discrepancy being generally attributed to dark matter halos. An alternative hypothesis is that accelerations in very weak gravitational fields are larger than predicted by Newton's laws, and there is no need for dark matter. Even though we do not currently have a satisfactory theory associated with this rival hypothesis, we can ask whether any observational tests could rule it out or prefer it over the dark matter hypothesis. Current evidence suggests that neither hypothesis enjoys a decisive advantage over the other. If dark matter turns out to be the correct interpretation however, then theories of galaxy formation face some quite severe fine-tuning problems.
     
  20. Feb 16, 2004 #19

    wolram

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    i have attempted to give a background to my skepticism
    for dark matter, especially (non baryonic) the papers i have posted
    may only scratch the confidence of people that believe in
    its existence, but i am far from concluding it is a
    reality, if anyone has a contribution to this thread
    it would be most welcome.
     
    Last edited: Feb 16, 2004
  21. Feb 16, 2004 #20

    wolram

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    posted by MARCUS.

    I wish we had Nereid's advice on this.
    -------------------------------------------------------------------
    i am in total agreement, if anyone has an explanation for
    the negative or null resuls for DM i expect it would be
    NERIED.
     
  22. Feb 16, 2004 #21

    wolram

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    http://www.scienceagogo.com/news/20010225075625data_trunc_sys.shtml

    This invisible matter is sometimes called dark matter and sometimes referred to as the missing mass. Some experts argue that it is simply ordinary matter (what scientists call baryonic matter) that is too cold to glow. Others maintain that not enough ordinary matter was made when the universe was created to account for all the dark matter that must exist so it must be made of something far more exotic. Now, a careful star survey conducted by an international team of astronomers, including Didier Saumon from Vanderbilt University, has concluded that a significant portion of the dark matter that forms an invisible halo around the Milky Way galaxy is made up of something very prosaic: dead stars, dim celestial objects called cool white dwarfs.
     
  23. Feb 19, 2004 #22

    wolram

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    http://www.universetoday.com/am/publish/dark_energy_doubts.html


    ESA's X-ray observatory, XMM-Newton, has returned tantalising new data about the nature of the Universe. In a survey of distant clusters of galaxies, XMM-Newton has found puzzling differences between today's clusters of galaxies and those present in the Universe around seven thousand million years ago. Some scientists claim that this can be interpreted to mean that the 'dark energy' which most astronomers now believe dominates the Universe simply does not exist…
     
  24. Feb 19, 2004 #23

    wolram

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    http://www.nsf.gov/od/lpa/news/04/pr0403.htm [Broken]

    Evidence from the Sloan Digital Sky Survey (SDSS) that at least a few ultra-massive black holes had come into existence less than a billion years after the universe began in the Big Bang, some 13.7 billion years ago. Each of these black holes is several billion times more massive than stars like our own Sun, and is sitting in the middle of an otherwise normal galaxy, swallowing up the surrounding gas and dust; the thermonuclear energy released in that process is visible to the SDSS astronomers as a brilliant, but very distant, point of light known as a quasar. The puzzle is that the SDSS black holes are as large as any ever seen, including those observed in nearby quasars that are much older. So how did they manage to form and grow to such a size before the universe was a tenth its present age? "The formation should have taken time," says Michael A. Strauss of Princeton University, who is the scientific spokesperson for the SDSS project and a co-principal investigator on this study. A formal report will be published in the Astronomical Journal in March 2004. A press release is available online at http://www.sdss.org/news/releases/20031217.lensing.html.
     
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  25. Feb 19, 2004 #24

    wolram

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    http://www1.elsevier.com/gej-ng/10/33/29/26/21/22/abstract.html [Broken]

    Self-consistent simulations of the interaction of initially spherical low-mass satellite galaxies with a massive Galactic dark halo suggest that observed apparent high mass-to-light ratios, (M/L)obs, in dwarf-spheroidal (dSph) satellites may be obtained through successive and destructive perigalactic passages.

    The model satellites are disrupted after several perigalactic passages, but orbiting condensations in phase space can clearly be identified as remnants well after this event. An intrinsic (M/L)true<3 leads to long-lived model remnants that show, as seen from Earth, a tantalizingly close resemblance to observed dSph satellites with (M/L)obs>10. The reason for large (M/L)obs is that the remnants have non-isotropic velocity dispersions, are non-spherical and are not in dynamical equilibrium. The remnants fade with time (i.e. orbital phase) and (M/L)obs increases indicating a correlation between brightness and (M/L)obs as in the observed dSph sample. The observed correlation between central surface brightness and integrated absolute magnitude is also approximately reproduced by model remnants of different dynamical age. A possibly useful method for probing the line-of-sight extension of a dSph galaxy is suggested.

    If it is true that most if not all dSph satellites are tidally modified remnants without dark matter then it is plausible that their progenitors may have formed as satellite galaxies in tidal tails during possible early merging events.
     
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  26. Feb 20, 2004 #25

    wolram

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    http://www.nytimes.com/2004/01/08/science/08ASTR.html?ex=1077426000&en=9b8dfb8f1b0b405d&ei=5070




    New-Found Old Galaxies Upsetting Astronomers' Long-Held Theories on the Big Bang
    By KENNETH CHANG

    Published: January 8, 2004


    TLANTA, Jan. 7 — Gazing deep into space and far into the past, astronomers have found that the early universe, a couple of billion years after the Big Bang, looks remarkably like the present-day universe.

    Astronomers said here on Monday at a meeting of the American Astronomical Society that they had found huge elliptical galaxies that formed within one billion to two billion years after the Big Bang, perhaps a couple of billion years earlier than expected.

    A few days earlier, researchers had announced that the Hubble Space Telescope had spotted a gathering cloud of perhaps 100 galaxies from the same epoch, an early appearance of such galactic clusters.

    On Wednesday, astronomers at the meeting said that three billion years after the Big Bang, one of the largest structures in the universe, a string of galaxies 300 million light-years long and 50 million light-years wide, had already formed. A light-year is the distance that light travels in one year, or almost six trillion miles.

    That means the string is nearly 2,000 billion billion miles long.

    Some astronomers said the discoveries could challenge a widely accepted picture of the evolution of the universe, that galaxies, clusters and the galactic strings formed in a bottom-up fashion, that the universe's small objects formed first and then clumped together into larger structures over time.

    "The universe is growing up a little faster than we had thought," said Dr. Povilas Palunas of the University of Texas, one of the astronomers who found the string of galaxies. "We're seeing a much larger structure than any of the models predict. So that's surprising."

    In the prevailing understanding of the universe, astronomers believe that slight clumpiness in the distribution of dark matter, the 90 percent of matter that pervades the universe but still has not been identified, drew in clumps of hydrogen gas that then collapsed into stars and galaxies, the first stars forming about a half billion years after the Big Bang. The galaxies then gathered in clusters, and the clusters gathered in long strings with humongous, almost empty, voids in between. The first such string, named the Great Wall, was discovered in 1989 about 250 million light-years away.

    The newly discovered string lies in a southern constellation, Grus, at 10.8 billion light-years away, and represents what the universe looked like 10.8 billion years ago, or three billion years after the Big Bang.

    The international team of researchers identified 37 very bright galaxies in that region of space and found that they were not randomly distributed, as would be expected, but instead appeared to line up along the string.

    Such structures are rarely seen in computer simulations of the early universe, said Dr. Bruce E. Woodgate of the NASA Goddard Space Flight Center, a member of the team.

    "We think it disagrees with the theoretical predictions in that we see filaments and voids larger than predicted," Dr. Woodgate said.

    Dr. Robert P. Kirshner of the Harvard-Smithsonian Center for Astrophysics said the findings were interesting, but that it was too early to eliminate any theories. What is probably needed was a better understanding how of a clump of dark matter leads to the formation of stars.

    "What we're seeing here," Dr. Kirshner said, "is the beginning of the investigation how structure grows."

    At the astronomy meeting on Monday, another team of researchers reported finding a large number of large elliptical galaxies. As part of an investigation known as the Gemini Deep Deep Survey, the astronomers explored 300 faint galaxies dating from when the universe was three billion and six billion years old. The large elliptical galaxies are supposedly a merged product of smaller spiral galaxies.

    Yet not only did they exist that early in the universe, but the stars within these galaxies also appeared a couple of billion years old already, implying that they had formed as early as a billion and a half years after the Big Bang.

    "Massive galaxies seem to be forming surprisingly early after the Big Bang," said Dr. Roberto Abraham of the University of Toronto and a co-principal investigator on the team. "It is supposed to take time. It seems to be happening right away."
    -------------------------------------------------------------------

    The data actually fit better with the views that astronomers held before the rise of the current dark-matter models, when they theorized that the largest galaxies formed first.
    --------------------------------------------------------------------

    "If we presented this to astronomers 25 years ago," Dr. Abraham said, "they wouldn't have been surprised."
     
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