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 radio-loud and ∼26–34 γ-ray-selected γ-ray pulsars, which can be detected with a γ-ray flux Fγ ⩾ 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 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 Fγ ⩾ 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 Fγ ∼ 10−11 erg cm-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.