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Lensed quasar observations support dark matter models

  1. Dec 18, 2003 #1

    Nereid

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    SDSS observations, supported by Subaru and Keck, confirmed that a massive cluster of galaxies is the gravitational lens for a quadruple-quasar image, the widest pair being separated by >14" (arc seconds).

    In addition, "[d]iscovering one such wide gravitational lens out of over 30,000 SDSS quasars surveyed to date is perfectly consistent with theoretical expectations of models in which the universe is dominated by cold dark matter. This offers additional strong evidence for such models," (Masamune Oguri, University of Tokyo, one of the researchers).

    http://www.sdss.org/news/releases/20031217.lensing.html
     
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  3. Dec 18, 2003 #2

    wolram

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    The fact that these quasars are not lensed says that astronomers have to take seriously the idea that quasars a few billion times the mass of the Sun formed less than a billion years after the Big Bang", said Richards. "We're now looking for more examples of high-redshift quasars in the SDSS to give theorists even more supermassive black holes to explain."
    ----------------------------------------------------------------------
    maybe we have to reconsider some theories?
     
  4. Dec 18, 2003 #3

    wolram

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    if this BH is not at the very edge of the universe it
    would suggest that even older ones could exist, this
    begs the question, how much less than a billion YRs
    could the first supermassive BHs have formed?
     
  5. Dec 18, 2003 #4

    Nereid

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    Yes! :smile: Lots of work to be done; JWST, we need you!!
     
  6. Dec 18, 2003 #5

    marcus

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    that link was to two papers
    Masamune Oguri----a 15 arcsecond lensing that statistically agrees with the estimate of dark matter

    Gordon Richards----checking that a sample of 4 quasars are not lensed.

    the second one doesnt change the picture dramatically. it remains difficult to understand how all those supermassive black holes can have formed in the first billion years, at least if you go by the experience of our galaxy and the nearby ones we can see slowly evolving

    Nereid please elucidate if you can----we know the MW is currently gobbling up some smaller galaxies----we see large clusters of galaxies in which the big ones are gobbling up the smaller ones.
    but MW has been around for a long time and still has not developed a supermassive BH
    our central BH is only like 2 or 3 million solarmasses IIRC
    Please confirm, the problem then is how did all those primordial galaxies SUCCEED in forming SMBHs, presumably by the same sort of random gobbling up of smaller ones that is still going on, when the galaxies of for example Virgo Cluster have so far failed? Was anything statistically different back then to give them better odds?

    My guess is that this problem will be settled peaceably within the confines of mainstream astronomy, by gradually assembling a better picture of conditions back then-----the U was DENSER back then and doubtless did give them better odds at assembling into a supermassive.
    Which I do not envy. I like our setup fine as it is.

    What I find more interesting though is the first paper in Nereid's link.

    Again it arises from someone calculating some odds. This time it is how abundant or rare should lensed quasars be (of various angular sizes) if the amount of dark matter is what it is estimated to be.
    Am I being boring, just repeating stuff. It seems intriguing. I will get a number and come back.
     
  7. Dec 18, 2003 #6

    marcus

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    Nereid I am a bit uncertain of my interpretation so would
    help if you confirm or correct any gross error
    IF the estimate is correct that dark matter is 23percent to visble's 4 percent then what that means is that
    everything we can see is 5 to 6 times heavier than it looks

    so we map out the distant objects and we see that there are X many of them that are 10 billion LY away and typically have a bunch of stuff between us and them that might lense (if it was massive enough)

    then we say that if the estimate is right and that stuff in between us is 5 or 6 heavier than it looks then in some number cases we should see lensing 7 arcseconds wide or less
    and in some smaller number of cases we should discover even wider like 10 arcseconds or more.

    then they go about looking and after a while they say LOOK we found umpteen cases of small lensing like 7 arcseconds wide and only one case of very wide lensing. this is in the right ratio to agree with the ODDS that we calculated.

    so we believe that galaxies are indeed 5-6 times more massive than they look and dark matter is 23 percent of the total...

    its not a blockbuster discovery but just one more little bit of confirmation that the estimate is working out. D'accord?
     
  8. Dec 18, 2003 #7

    Nereid

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    Exactement! That's what the first paper is; another small step towards constraining the values in the models. In some ways this is 'the boring phase' of the normal process - the only headlines it usually generates are when 'mainstream' is not confirmed.

    More on SMBHs later.
     
  9. Dec 19, 2003 #8

    wolram

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    two clips i found explaining that BH formed with the galaxy
    it inhabits
    --------------------------------------------------------------------

    http://www.space.com/scienceastronomy/starburst_blackhole_030403.html
    The rate of star birth calculated by the new study means a large, normal elliptical galaxy could form in just 100 million years or so. That is important, because other observations have shown that this must be the case, though astronomers have never seen the rapid rate of star formation in action until now.
    -----------------------------------------------------------
    http://www.msnbc.com/news/135107.asp
    “Now we know that every big galaxy has a big black hole and was probably formed at the same time and probably with some of the same processes which formed the galaxies themselves,” said Genzel.
     
  10. Dec 19, 2003 #9

    Nereid

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    wolfram, the first article is a good snapshot - on-going debate (and lots of observations) on whether the SMBH or the galaxy is the chicken or the egg, or perhaps it's more complicated.

    The observations are difficult, and it'll be quite a while before enough has been observed for us to be really comfortable, statistically speaking.

    The second paper in the SDSS article illustrates this well (I've not read the original yet, so I'm only going by what's in the link I posted). With Hubble, no lensing object could be found for those four bright, distant quasars. That's surely an interesting finding, and the researchers probably did a sound statistical analysis too. But, it's still only four objects.

    Time for JWST* :smile:

    *JWST = James Webb Space Telescope (previously Next Generation Space Telescope, a.k.a. successor to Hubble):
    http://ngst.gsfc.nasa.gov/
     
  11. Dec 20, 2003 #10

    wolram

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    here are a few articles i found to help me understand
    subject, i havnt read them all yet.


    http://nedwww.ipac.caltech.edu/level5/March03/Courbin/Courbin4_4.html
    ----------------------------------------------------------------------------i cant access this data anyone a member?
    http://www.blackwell-synergy.com/links/doi/10.1046/j.1365-8711.2003.06256.x/abs/
    ----------------------------------------------------------------------------
    http://aanda.u-strasbg.fr:2002/articles/aa/full/2003/40/aa3444/aa3444.right.html
    Until recently only a few hundred quasar spectra were available for the detection of quasar absorbers. With the help of multi-fiber spectroscopy, surveys of thousands of quasars have become publicly available. A pioneer experiment in this area, the 2 degree field quasar redshift survey (2QZ) has already acquired more than 20 000 quasar spectra (Boyle et al. 2001; Croom et al. 2001a; Hoyle et al. 2002) and provides an unprecedented source for statistical studies of quasars in a homogeneous sample.
     
  12. Jan 10, 2004 #11

    Nereid

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    Here's an interesting source of data that we may use:
    http://www.stsci.edu/ftp/science/goods/transients.html

    If we could use these images as Ragazzoni, Turatto and Gaessler used the HST one of SN1994D, we could push the same constraint on quantum blurring out by at least a factor of 30 (to >500 Mpc).

    If the ESSENCE* team has its way, within a few years we'll be swamped with high quality data!
    http://www.ctio.noao.edu/wproject/

    *"Equation of State: SupErNovae trace Cosmic Expansion " aka "the w project"
     
  13. Jan 12, 2004 #12

    wolram

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    its amazing what can be accomplished in 15 nights per
    year,and the amount of information coming from these
    observations to the web, i have marked the ESSENCE page
    for future use.
     
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