Origin of cosmic gamma ray background

  • Thread starter wolram
  • Start date
  • #1
wolram
Gold Member
4,267
557

Main Question or Discussion Point

http://arxiv.org/abs/astro-ph/0506520

Title: Dark Matter Annihilation: the origin of cosmic gamma-ray background at 1-20 MeV
Authors: Kyungjin Ahn Eiichiro Komatsu
Comments: 5 pages, 3 figurs; submitted to PRD, Rapid Communication

The origin of the cosmic gamma-ray background at 1-20 MeV remains a mystery. We show that gamma-ray emission accompanying annihilation of 20 MeV dark matter particles explains most of the observed signal. Our model satisfies all of the current observational constraints, and naturally provides the origin of "missing" gamma-ray background at 1-20 MeV and 511 keV line emission from the Galactic center. We conclude that gamma-ray observations support the existence of 20 MeV dark matter particles. Improved measurements of the gamma-ray background in this energy band undoubtedly test our proposal.
 
Last edited:

Answers and Replies

  • #2
Nereid
Staff Emeritus
Science Advisor
Gold Member
3,367
1
Good one wolfram!

I think this is the key phrase:
Our model satisfies all of the current observational constraints
Unfortunately, the present observational constraints are pretty mild indeed.

File this in the 'worth watching, review again when a lot more data becomes available' file?
 
  • #3
hellfire
Science Advisor
1,047
1
If annihilation events of dark matter particles with antiparticles take place in the present universe, then annihilation events should have been more frequent in past (due to higher density). This implies a background of radiation with wavelengths down to 1/z times (lets say 0.001, since recombination) the wavelength of the current gamma ray background. Shouldn't this be observable?
 
  • #4
Nereid
Staff Emeritus
Science Advisor
Gold Member
3,367
1
hellfire said:
If annihilation events of dark matter particles with antiparticles take place in the present universe, then annihilation events should have been more frequent in past (due to higher density). This implies a background of radiation with wavelengths down to 1/z times (lets say 0.001, since recombination) the wavelength of the current gamma ray background. Shouldn't this be observable?
Not necessarily.

First, if it's a 'line', then what line?

Second, the ancient 'space density' of DM recombination radiation has no strong constraints (unless the DM annihilation cross sections, densities, etc are well-constrained), so a lack of detection would put only the mildest limits on the parameter space (OK, I've not done the calculations; I'm working off the top of my head).

Finally, what do we know about the evolution of DM - particles, clumps, etc? I mean, for example, hasn't DM become more clumped (through self-gravity and baryonic clumping) through time than less?
 
  • #5
Chronos
Science Advisor
Gold Member
11,408
738
I'm sort of fond of the dark matter annihilation explanation. It is so convenient, I worry it might be too good to be true. Will report back after doing some homework.
 
  • #6
Garth
Science Advisor
Gold Member
3,574
105
May the gamma-ray background be modelled by a background of GRB's? The most likely model for those, based on the SWIFT observation, is that of a binary neutron star fusion into a BH.

Garth
 
  • #7
wolram
Gold Member
4,267
557
Nereid said:
Good one wolfram

.File this in the 'worth watching, review again when a lot more data becomes available' file?
Yes this seems to swing the swingometer to i am wrong, but as you say it is
to soon to be sure.
 

Related Threads on Origin of cosmic gamma ray background

  • Last Post
Replies
3
Views
4K
  • Last Post
Replies
14
Views
3K
Replies
6
Views
3K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
2
Views
1K
Replies
3
Views
860
  • Last Post
Replies
1
Views
2K
Top