[Shape-univ] INTEGRAL/SPI: first 511keV-photograph of dark matter halo?

[Boud Roukema]

Witam,

On Tue, 6 Jun 2006, Bartosz Lew wrote:

> Is this something new ? The peper is like from one year ago.

No, but i hadn't seen it before.

> > Kn\"odlseder et al. (2005) seems to be the main "discovery" article of
> > the INTEGRAL/SPI results.
> >
> > It has some very nice pictures - especially Figs 4, 5 and 7 - here i've
> > put the closed links, but the figures are in the astro-ph versions too,
> > of course:
> >
> > Fig 4
> > http://www.edpsciences.org/articles/aa/full/2005/38/aa2063-04/img62.gif
> >
> > Fig 5
> > http://www.edpsciences.org/articles/aa/full/2005/38/aa2063-04/img63.gif
> >
> > Fig 7
> > http://www.edpsciences.org/articles/aa/full/2005/38/aa2063-04/img108.gif
> >
> > We may soon be able to say that Fig.~4 was the "first picture of
> > invisible matter" ;).
>
> well, it's a picture of what's left of it:  electrons, positrons
> ... and protons, neutrinos, etc.
>
> I didn't have time to read this carefully, but what are the principles of
> the measurment giving hint on variation of fine structure constant ?

http://arXiv.org/abs/astro-ph/0507142

IIUC (if i understand correctly):

* introduction
LDM hypothesis to explain INTEGRAL/SPI
  =>  mass estimated < 100 MeV
  => "scalar particle" coupled to light Z' boson

* sections 2, 3, 4 lead to:

* 5.1 "scalar particle" coupled to light Z' boson AND
      "scalar particle" coupled to heavy fermion

* 6.3 there is some small difference f(10^{-11})  [the function f is not given]
between alpha measured by the Quantum Hall experiment

 http://en.wikipedia.org/wiki/Quantum_Hall_effect

and a "theoretical" estimate made assuming the standard model of p.p. including QED
and the results of the "g-2" muon experiments related to supersymmetry testing:

 http://en.wikipedia.org/wiki/Supersymmetry#Muon_g.E2.88.922_experiment

The authors say that this difference could be due to different precision levels
in the QH versus the experiments contributing to the QED "theoretical" estimate.

Equality between the two is obtained for m_LDM \sim 3-9 MeV.


In other words: the QH and g-2 experiments give different results for alpha.
The difference is not (yet) statistically significant, but a light scalar coupled to
a heavy particle, needed for the LDM hypothesis, would give this difference
for m_LDM \sim 3-9 MeV.  (The real mass might be higher since this assumes
smooth distribution of matter in the DM halo, ignores the fact that some part
of the emission might be from point sources, etc.)

So improvements in the QH effect experiments could support the LDM hypothesis
and explain the present possible discrepancy in alpha estimates.

This is, coincidentally(?), roughly on the same order of magnitude as
the alpha evolution claims in quasar absorption systems, since the QSO
claims were of order 10^{-6} or over \sim 5 billion yr or
so, and if convert this to 8kpc = 3000yr then we get

delta(alpha)/alpha \sim 10^{-12} between the Sun and the GC.

However, the last i remember of the QSO abs sys alpha evolution claims they
were no longer looking interesting (one of Srianand's papers is pretty
convincing - look in shape-univ and/or cosmo-torun archives... :). In any case,
a more precise calculation would be needed to see if these really are on
the same scale or whether i've rounded off too many orders of magnitude.



BTW, the estimate of the inner part of the MW DM profile is quite tight:
* section 5.2   \gamma \gtapprox 1.03\pm 0.04

Again, clustering, contamination, etc. make this a lower limit only.


pozdr
boud



> > Ascasibar et al 2005 has some very interesting conclusions - apart from
> > the continued validity of LDM as only (so far) viable explanation, they say:
> >
> >>  One consequence is that the value of the fine structure constant \alpha
> >> should differ from that recommended in the CODATA (Committee on Data
> >> for Science and Technology). This is a very strong test for the LDM
> >> scenario and an additional motivation in favour of experiments
> >> measuring \alpha directly. Our results finally indicate that an accurate
> >> measurement of the shape of the dark halo profile could have a
> >> tremendous impact on the determination of the origin of the 511-keV
> >> line and vice versa.
> >
> > Both of these are very good for showing that evidence should build up either
> > for or against the LDM hypothesis. :)
> >
> > pozdr
> > boud
> >
> >
> > Kn\"odlseder et al. (2005)
> > http://arXiv.org/abs/astro-ph/0506026
> > http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?bibcode=2005A%26A...441..513K&db_key=AST
> >
> > Ascasibar, Y et al. (2005)
> > http://arXiv.org/abs/astro-ph/0507142
> > http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?bibcode=2006MNRAS.368.1695A&db_key=AST
> >
> >
> >
>
>