EGRET Unidentified Sources and the Galactic Spiral Arms

An unbiased and complete LogN-LogS relation samples the source distribution for a specific source geometry without the knowledge of the source luminosity function or the distance. Based on such an analysis we show that EGRET unidentified (EUI) sources are very closely aligned with the Galactic spiral arms and specifically with the distribution of the giant molecular clouds. Furthermore, the luminosity distribution of the unidentified sources show a two population Gaussian distribution. We find that a combined distribution of OB associations, SNR and superbubbles interacting with molecular clouds within the spiral arms are the most likely counterparts of the unidentified sources.