There are several small satellite galaxies of milky way. Namely, Draco, Sextans, Carina, Fornax and others. What do we know about how dark matter is distributed in these satellites? Do we know about the amount of dark matter contained in these galaxies?
Any technical or non-technical information is welcome.
0603775 is discussing halo with small core or cusp
0910.3538 is stating that dwarf galaxies has a uniform core.
But expected distribution is sharply falling. It is also referring to
a core/cusp problem.
In simple terms, what is the core/cusp problem ?
Biswajoy,
As I understand, simulations of halos comprised of cold dark matter particles (which must interact gravitationally, but should not interact electromagnetically since they cannot be detected) indicate that they should produce very high densities at their centers - densities that, to varying extents, disagrees with observations of galaxies and galaxy clusters, some of which seem to indicate that their CDM halo is cored - of lower than average density at its center.
See http://en.wikipedia.org/wiki/Cuspy_halo_problem and http://arxiv.org/abs/astro-ph/0102349. Also see http://dx.doi.org/10.1155/2010/789293 and http://dx.doi.org/10.1088/2041-8205/736/1/L2 for more detailed discussions.
Paper of Lam Hui is referring to a annihilation of dark matter particles.
In a high density core two dark matter particles can interact with each
other and annihilate to photons (perhaps). Then one can detect gamma
rays from the CORE of a galaxy, I guess. If they annihilate to something
in the dark sector then we cannot observe them.
de Blok's article is explaining core/cusp problem. As cosmological
simulations give steeply falling power law behavior of dark matter
it is contradicting observations of dwarf galaxies. In the latter case
direct observation is indicating a constant density dark matter core.
What I understand from his review is that
If rho varies as r^alpha power law then
alpha=-1 ---> cusp models
alpha=0 ---> core models
Here is an article on dark matter in dwarf galaxies: http://arxiv.org/abs/1011.0899
and http://arxiv.org/abs/0810.2125
As I understand, the appendix of the second article shows optical image of the galaxies compared with velocity dispersion. See for example page 39. perhaps this gives a good impression of dark matter distribution (like rotation curves)
Gunther,
Could you tell me that when I am making a simulation of dark matter
profile, do I take into account only gravitational interaction with dark matter ?
Else if there is an ordinary dark interaction other than gravity (for
example Neutralino has a weak interaction which is a short range force)
will results change ?
Usually, only the gravitational interaction of dark matter is taken into account (so far as I know), since the cold dark matter is used to explain the missing mass in a galaxy (to explain the rotation curve). I dont believe that a short range force will change the results essentially. But the idea is interesting, maybe it's worth a try.
Biswajoy,
As I understand, if one assumes that the dark matter is cold (CDM), it's considered to interact only through gravitation. Self-gravitation in CDM-only simulations produces the cuspy-halo problem, which is, I think, most often ignored.
The prior reference, http://en.wikipedia.org/wiki/Cuspy_halo_problem, concludes:
"One approach to solving the cusp-core problem in galactic halos is to consider models that modify the nature of dark matter; theorists have considered warm, fuzzy, self-interacting, and meta-cold dark matter, among other possibilities."
See: http://en.wikipedia.org/wiki/Warm_dark_matter
http://arxiv.org/abs/astro-ph/0003365
http://en.wikipedia.org/wiki/Self-interacting_dark_matter
http://arxiv.org/abs/astro-ph/0606281
http://dx.doi.org/10.1086%2F511807
Sterile neutrino is a possibility as MiniBooNE has detected it with
some confidence. But they are not enough sure (5 sigma) to claim
that they have discovered sterile neutrino. At LSND the sterile neutrino
mass squared difference was 1eV^2. But let us see if that changes when
real fit is a combined fit of LSND and MiniBooNE. Such a thing happened
during the SNO experiments in SUDBURY lab a decade or so ago. At
that time people believed in the small mixing solution (SMA), but
when the combined fit along with SNO data was published it was a
LMA solution and not SMA. As far as I understand KeV sterile
neutrino is a good dark matter candidate.
An interesting new paper in this area has appeared recently,
"Dark matter heats up in dwarf galaxies"
J. I. Read, M. G. Walker, P. Steger,
https://arxiv.org/pdf/1808.06634v1.pdf
This paper shows an apparent correlation of star formation rate (of visible sector) with dark matter density profile. Essentially it's a pointer to the fact that there are interactions between visible and dark sector. A careful analysis of such data samples can reveal the nature of visible-dark interaction.
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