Fermi team: Catalogue of gamma-ray sources at energies above 10 GeV

Sky map of gamma-ray counts above 10 GeV in Galactic coordinates in Hammer-Aitoff projection. 

The binning is 0.◦5 and the image has been smoothed with a 2-dimensional Gaussian of full width at half maximum 0.◦75. 

Credit: arXiv:1306.6772 [astro-ph.IM]

The team of scientists associated with the Fermi Gamma-ray Space Telescope mission has published a catalog of gamma-ray sources at energies above 10 GeV. 

In their paper uploaded to the preprint server arXiv, they outline the various sources of gamma-ray emissions above 10 GeV detected by the Gamma-Ray Space Telescope (GLAST) currently orbiting the Earth.

Because it's in orbit, the LAT is capable of looking at space from every direction—it can read data from the entire cosmos in just three hours and does so over and over all day long, every day.

In this new catalog, the researchers present data from the first three years of the telescope's mission—focusing specifically on the energy range above 10 gigaelectronvolts, which they note hasn't been adequately outlined in prior catalogs.

The team explains that this new catalog is meant to serve as a bridge between other catalogs created using data received from the GLAST (which generally have thousands of sources) and ground-based telescopes.

It offers a new way to look at the higher energy gamma ray emissions and hopefully will help to identify those that are still unknown.

Also, the team sees their catalog as an opportunity to help identify which sources are also emitting other types of radiation at high energy levels.

The team notes that the telescope detected a total of 514 10 GeV sources—the catalog details the location of each, its spectra and any associations with other cataloged sources.

They add that 449 of the sources noted have previously been associated with a known source, leaving 65 of them described as "unassociated."

The team doesn't know what is causing the emissions—they suggest they might be previously unknown classes of objects. Others in the field have suggested they could be "dark galaxies" which are galaxies rich in dark matter.

Those sources that have been previously associated with known entities include active galactic nuclei, blazers, and pulsars.

The team says that although the proportion of unassociated sources is lower than prior catalogs created, they plan to follow up on those listed in this new catalog with the hope of eventually identifying them as well.

More information: The First Fermi-GLAST Catalog of Sources Above 10 GeV, arXiv:1306.6772 [astro-ph.IM] arxiv.org/abs/1306.6772