POPULATION STUDY FOR gamma-RAY PULSARS WITH THE OUTER GAP MODEL

Inspired by the increase of the population of gamma-ray emitting pulsars by the Fermi telescope, we perform a population study for gamma-ray emitting canonical pulsars. We use a Monte Carlo technique to simulate the Galactic population of neutron stars and the radio pulsars. For each simulated neutron star, we consider the gamma-ray emission from the outer gap accelerator in the magnetosphere. In our outer gap model, we apply the gap closure mechanism proposed by Takata et al., in which both photon-photon pair-creation and magnetic pair-creation processes are considered. Simulating the sensitivities of previous major radio surveys, our simulation predicts that there are similar to 18-23 radio-loud and similar to 26-34 gamma-ray-selected gamma-ray pulsars, which can be detected with a gamma-ray flux F-gamma >= 10(-10) erg cm(-2) s(-1). Applying the sensitivity of the six month observation of the Fermi telescope, 40-61 radio-selected and 36-75 gamma-ray selected pulsars are detected within our simulation. We show that the distributions of various pulsar parameters for the simulated gamma-ray pulsars can be consistent with the observed distribution of the gamma-ray pulsars detected by the Fermi telescope. We also predict that similar to 64 radio-loud and similar to 340 gamma-ray-selected pulsars irradiate the Earth with a flux F-gamma >= 10(-11) erg cm(-2) s(-1), and most of those gamma-ray pulsars are distributed with a distance greater than 1 kpc and a flux F gamma similar to 10(-11) erg cm(-2) s(-1). The ratio between the radio-selected and gamma-ray-selected pulsars depends on the sensitivity of the radio surveys. We also discuss the Galactic distribution of the unidentified Fermi sources and the canonical gamma-ray pulsars.