Re: Dark Matter, QSOs and Microlensing
- From: "rloldershaw@xxxxxxxxxxx" <rloldershaw@xxxxxxxxxxx>
- Date: Wed, 30 Aug 2006 23:07:17 +0000 (UTC)
[ Mod. note: Removed cross post to sci.math.research, as it's really
not on topic there. -ik ]
Phillip Helbig---remove CLOTHES to reply wrote:
The problem with the Local Group in this context is that it is small
relative to the universe, so it is difficult to extrapolate any density
of compact objects to get a fraction of dark matter on the cosmological
scale.
Dark matter on a galactic scale, i.e. that necessary to explain rotation
curves, or dark matter in the sense of the difference between the
cosmological Omega value (0.3 or so) and the small fraction accounted
for by luminous matter (or, in a slightly different definition, the
fraction in baryonic matter)?
I think we may be in agreement that QSO research has yielded some
interesting hints that a lot of something massive is in and between
galaxies, but that the QSO variability results have always been too
ambiguous for the astrophysical community to fully accept.
One area we have not mentioned is X-ray background observations. Lots
of unidentified point-sources have been detected and their numbers
increase as you go to lower luminosities (fainter objects). Large
populations of low-mass Kerr-Newman black holes would presumably be low
level X-ray emitters due to low level ISM and IGM accretion. We may
already have solid evidence of their existence and abundance in our
hands, but we don't yet know how to interpret it. Advances with
existing observatories have slowly and steadily been moving towards an
understanding of the enigmatic X-ray background, but it may take a new
generation of improved X-ray observatories to sort this out.
My rule-of-thumb assumption is that dark matter roughly follows
luminous matter in distribution and abundance. Although there are
probably lots of stellar-mass dark matter objects in the "voids"
between galactic clusters, I suspect the overwhelming numbers of these
objects are exactly where they have been found so far: within galaxies
and clusters of galaxies. My guess is that when we have solved the
galactic dark matter problem, that will constitute the complete
solution to all aspects of the dark matter enigma. But this will have
to be demonstrated observationally.
Bottom line research strategy: if we can find out the nature of the
dark matter in the Local Group, then we will probably know the general
nature of the dark matter for other galaxies thoroughout the Universe,
and we will be able to draw reasonable conclusions about the dark
matter that is probably ejected from galaxies and culsters and which
probably roams intergalactic space at very high velocities and low
densities. The most important learning begins at home.
.
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