Bartosz Lew Bartosz.Lew w astri.uni.torun.pl
Pon, 12 Sty 2004, 18:14:08 CET

> i'm not sure if it helps for a research project...

if the project is about getting some clues about DM halo density profile
then the first question is, what dataset to use, which is related to what
we want do calculate. as I understand it's like:

for distances < 50kpc Hi claudls can be used, and stellar kinematics,
for distances < 100 kpc gravitational lensing is in use
for dist. < 1Mpc study of that sattelite galaxies mae be used. (SDSS etc.)
oh and there is also that X-ray flux approach for whole clusters of
galaxies. (but don't know how this works, some assumptions about flux -
mass or luminosity - mass must be made)

all of the above techniques require powerfull cpu consuming simulations
and involve gaz/hyrdo/sometimes magneto/radiative and DM  dyanamics stuff.

otherwise I see (if only gravity is involved) no way to solve momentum
problem in galaxy disk formation. the cusps etc seem to be more vast
problem:
\rho ~ r^-x - this is the general law

- N-body simulations (with CDM) give density profiles which have x=1 - 1.5
- only disk stellar density declines exponentially or with x close to 0.25
(for bluge)
- flat rotation curve (so distances from about 10 to 50 kpc) constraint
give x=2 so
- obserwations velocity fields give (for these distances) x higher
(contrary to smoothed central cusp idea) and even higher x=3 for very
periphial galactic regions > 100 kpc
- but obserwations of dwarf galaxies give a flat density cores (so it's
for very small distances from the galaxy center)

totanisan's paper is also intersting to me.
but it  seems it's just the idea of self interacting DM (SIDM) which has
been studied in simulations to fit density profile to obserwations.

> - it seems that the long expected cooling flows in g clusters do not
exist

the cooling does not exist (because the disks of galaxies would be
too small then observed with simulated high cooling rate) unless there are
additional heating sources (agn, SIDM, UV background, starbursts ,etc,
second reionisation :))

bartek



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