Ahead of the first meeting of the astronomy twitter journal club on Thursday I thought I’d try to give a very brief overview of the chosen paper: Gamma Rays From The Galactic Center and the WMAP Haze. This will undoubtedly leave out many details – it’s not intended to be a substitute for actually reading the paper!
Recently, the Fermi Gamma-ray Space Telescope reported that it had seen an excess in gamma-rays coming from the centre of our galaxy, which couldn’t be accounted for by contamination from more distant objects. One possible cause of this, according to theorists, is the annihilation of WIMPs (Weakly Interacting Massive Particles) – a form of dark matter*.
If this is true, the annihilating WIMPs should produce electrons and positrons. These in turn would interact with the local magnetic field to create synchrotron radiation. The observed gamma-rays from Fermi place strong constraints on the behaviour of the dark matter particles, which in turn means that the amount of synchrotron radiation can be predicted.
The authors of the paper make this prediction and find it agrees well with the ‘haze’ seen around the centre of the Milky Way by the WMAP satellite. However, to do this they need to assume various strengths for the magnetic field in the region: they point out that better measurements of this would help tie down exactly what happens when the WIMPs annihilate.
I’ll leave the final word to the Colin Stuart who put this paper forward for discussion:
I chose this paper because it sparked a lot of debate when I wrote the research up for a physicsworld.com article. It initially grabbed my attention because it included a mention of the CoGeNT and DAMA/LIBRA potential dark matter signals. I had been following the debate over what exactly these experiments had detected and whether it was really dark matter or not. When this paper tried to pin the gamma-rays detected at the heart of the Milky Way to dark matter WIMPs of similar mass to these experiments I knew it would ruffle a few feathers. Then I heard that Astronomy Journal Club was starting up and I thought it would be great to open that debate up for further discussion.
*For an excellent recap on dark matter spend a couple of minutes watching this video from PhD Comics: