We present results of a pulsar population synthesis study that incorporates a number of recent developments and some significant improvements over our previous study. We have included the results of the Parkes multibeam pulsar survey in our select group of nine radio surveys, doubling our sample of radio pulsars. More realistic geometries for the radio and -ray beams are included in our Monte Carlo computer code, which simulates the characteristics of the Galactic population of radio and -ray pulsars. We adopted with some modifications the radio-beam geometry of Arzoumanian, Chernoff, and Cordes. For the -ray beam, we have assumed the slot gap geometry described in the work of Muslimov and Harding. To account for the shape of the distribution of radio pulsars in theṖ-P diagram, we continue to find that decay of the magnetic field on a timescale of 2.8 Myr is needed. With all nine surveys, our model predicts that EGRET should have seen seven radio-quiet (below the sensitivity of these radio surveys) and 19 radio-loud -ray pulsars. AGILE (nominal sensitivity map) is expected to detect 13 radio-quiet and 37 radio-loud -ray pulsars, while GLAST, with greater sensitivity, is expected to detect 276 radio-quiet and 344 radio-loud -ray pulsars. When the Parkes multibeam pulsar survey is excluded, the ratio of radio-loud to radio-quiet -ray pulsars decreases, especially for GLAST. The decrease for EGRET is 45%, implying that some fraction of EGRET unidentified sources are radio-loud -ray pulsars. In the radio geometry adopted, short-period pulsars are core dominated. Unlike the EGRET -ray pulsars, our model predicts that when two -ray peaks appear in the pulse profile, a dominant radio core peak appears in between the -ray peaks. Our findings suggest that further improvements are required in describing both the radio and -ray geometries.

No abstract

We present results of a population synthesis study of radio-loud and radio-quiet γ -ray pulsars from the Galactic plane and the Gould Belt. The simulation includes the Parkes multibeam pulsar survey, realistic beam geometries for radio and γ -ray emission from neutron stars and the new electron density model of Cordes and Lazio. Normalizing to the number of radio pulsars observed by a set of nine radio surveys, the simulation suggests a neutron star birth rate of 1.4 neutron stars per century in the Galactic plane. In addition, the simulation predicts 19 radio-loud and 7 radio-quiet γ -ray pulsars from the plane that EGRET should have observed as point sources. Assuming that during the last 5 Myr the Gould Belt produced 100 neutron stars, only 10 of these would be observed as radio pulsars with three radio-loud and four radio-quiet γ -ray pulsars observed by EGRET. These results are in general agreement with the recent number of about 25 EGRET error boxes that contain Parkes radio pulsars. Since the Gould Belt pulsars are relatively close by, the selection of EGRET radio-quiet γ -ray pulsars strongly favors large impact angles, β, in the viewing geometry where the off-beam emission from curvature radiation provides the γ -ray flux. Therefore, the simulated EGRET radioquiet γ -ray pulsars, being young and nearby, most closely reflect the current shape of the Gould Belt suggesting that such sources may significantly contribute to the EGRET unidentified γ -ray sources correlated with the Gould Belt.