Population study for γ-ray pulsars with the outer gap model

Abstract

Inspired by the increase of the population of γ-ray emitting pulsars by the Fermi telescope, we perform a population study for γ-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 γ-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 ∼18-23 radioloud and ∼26-34 γ-ray-selected γ-ray pulsars, which can be detected with a γ-ray flux F γ ≥ 10 -10 ergcm -2 s -1. Applying the sensitivity of the six month observation of the Fermi telescope, 40-61 radio-selected and 36-75 γ-ray selected pulsars are detected within our simulation. We show that the distributions of various pulsar parameters for the simulated γ-ray pulsars can be consistent with the observed distribution of the γ-ray pulsars detected by the Fermi telescope. We also predict that ∼64 radio-loud and ∼340 γ-ray-selected pulsars irradiate the Earth with a flux F γ ≥ 10 -11 erg cm -2 s -1, and most of those γ-ray pulsars are distributed with a distance greater than 1 kpc and a flux F γ ∼ 10 -11 ergcm -2 s -1. The ratio between the radio-selected and γ-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 γ-ray pulsars. © 2011. The American Astronomical Society.