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Density of the inter-cluster medium

  1. May 30, 2005 #1

    Garth

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    That is interesting ST. How dense is the inter-galactic-cluster medium?
    Garth
     
    Last edited: May 30, 2005
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  3. May 30, 2005 #2

    Nereid

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    This is a great question Garth ... and if I may add a rider: and how is such density measured/inferred?

    If you don't mind, I'd like to keep this thread to just QSO absorption lines (and closely related topics) - May I split this off as the start of a new thread?
     
  4. May 31, 2005 #3

    hellfire

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    WHIM stands for Warm-Hot Intergalactic Medium, a low density phase at 105 - 107 K, mainly located in the filaments and not part of any virialized system. About 30% - 40% of all baryons of the present universe (z < 2) were assumed to reside in this phase. It was postulated here and there is some observational evidence in the meanwhile.
     
    Last edited: May 31, 2005
  5. May 31, 2005 #4

    SpaceTiger

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    There are two main components to the intergalactic medium, the cold component (T<105 K) and the warm-hot component (105-107 K). The former is only a few times the critical density:

    [tex]\rho_c=\frac{3H^2}{8\pi G}[/tex]

    corresponding to a density of about 10-5 cm-3. The warm-hot component is about a factor of ten more dense than this. Finally, intracluster gas has densities of order 10-3 cm-3 and temperatures of around 107 K.

    You can determine these conditions from a lot of things, including fitting absorption lines in quasar spectra, looking at X-ray emission and absorption, and the Sunyaev-Zeldovich effect.
     
    Last edited: May 31, 2005
  6. May 31, 2005 #5

    Garth

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    These densities seem very high ST - with the critical density at around 10-29 cm-3?

    Nereid yes please let's start another thread.

    Garth
     
  7. May 31, 2005 #6

    SpaceTiger

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    That's 10-29 g cm-3. I was quoting densities in terms of atoms per unit volume (instead of mass per unit volume).
     
  8. May 31, 2005 #7

    Garth

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    Doh!!
    Homer

    Sometimes I just read too fast for my brain to catch up with my eyes.

    ST what's that in real money? i.e. in terms of gms.cm-3 and as a component of Omega?

    Garth
     
    Last edited: May 31, 2005
  9. May 31, 2005 #8

    SpaceTiger

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    The cold component corresponds to, as you said, about 10-29 g cm-3. The other two are a factor of 10 and 100 larger, respectively.

    In terms of omega, it depends on the redshift you're referring to. I don't know the numbers off the top of my head, but I'll look it up later.
     
    Last edited: May 31, 2005
  10. Jun 1, 2005 #9

    Nereid

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  11. Jun 1, 2005 #10

    Garth

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    Thank you Neried.

    The first question is that of the inventory of the IGM and the contribution it makes to the total Omega density parameter of the universe; that is both of baryonic and non-baryonic dark matter.

    We have cold gas clouds that leave the Lynman forest imprint on distant quasar spectra, WHIM (Warm/Hot Intergalactic Matter), primordial or otherwise Black Holes and any member of the exotic particle zoo that you care to dream up! Anything else I have forgotten? Ah yes! and a Dark Energy contribution; any way of measuring this?

    Garth
     
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