γ-Ray Pulsars and Massive Stars in the Solar Neighborhood

We revisit the association of unidentified Galactic plane EGRET sources with tracers of recent massive star formation and death. Up-to-date catalogs of OB associations, SNRs, young pulsars, HII regions and young open clusters were used in finding counterparts for a recent list of EGRET sources. It has been argued for some time that EGRET source positions are correlated with SNRs and OB associations as a class; we extend such analyses by finding additional counterparts and assessing the probability of individual source identifications. Among the several scenarios relating EGRET sources to massive stars, we focus on young neutron stars as the origin of the γ-ray emission. The characteristics of the candidate identifications are compared to the known γ-ray pulsar sample and to detailed Galactic population syntheses using our outer gap pulsar model of γ-ray emission. Both the spatial distribution and luminosity function of the candidates are in good agreement with the model predictions; we infer that young pulsars can account for the bulk of the excess low latitude EGRET sources. We show that with this identification, the γ-ray point sources provide an important new window into the history of recent massive star death in the solar neighborhood. Subject headings: pulsars — gamma rays — HII regions — OB associations — SNRs