Mattia Fornasa, Enzo Branchini, Lidia Pieri and I have been studying the flux and the angular power spectrum of gamma-rays produced by Dark Matter (DM) annihilations in the Milky Way (MW) and in extra-galactic halos.

The annihilation signal receives contributions from: a) the smooth MW halo, b) resolved and unresolved substructures in the MW, c) external DM halos at all redshifts, including d) their substructures. Adopting a self-consistent description of local and extra-galactic substructures, we have shown in a recent paper that the annihilation flux from substructures in the MW dominates over all the other components for angles larger than O(1) degrees from the Galactic Center, unless an extreme prescription is adopted for the substructures concentration.

We have also computed the angular power spectrum of gamma-ray anisotropies and found that, for an optimistic choice of the particle physics parameters, an interesting signature of DM annihilations could soon be discovered by the Fermi LAT satellite at low multipoles, l10^4 solar masses.

The Opening ceremony of the International Year of Astronomy will take place in Paris, January 15-16, 2009, under the aegis of the UN, the UNESCO (United Nations Educational, Scientific and Cultural Organisation) and the IAU (International Astronomical Union).

You can find the program (and live streaming) of the conference here, and more information on project, activities and events organised in the framework of the IYA here.

The Fermi satellite has discovered 12 new gamma-ray-only pulsars. You can find more information on the NASA website , or read the corresponding Symmetry Breaking Blog entry.

From the website of the European Space Agency:

“This satellite image, acquired by Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument on 7 January 2009, shows most of central and northern France covered by a white layer of snow, while regions closer to the Atlantic coast remain largely snow free. Towards the upper right Paris can just be seen under the cloud layer at the top edge of the image.

Credits: ESA”