Gamma-ray emission properties from mature pulsars in the galaxy and in the Gould Belt

We study the gamma-ray emission properties of pulsars by using a new self-consistent outer gap model. The outer gap can exist in pulsars older than 1 million yr if the effect of magnetic inclination angle, as well as the average properties of the outer gap, are considered. The mature gamma-ray pulsars, whose ages are between 0.3 and 3 million yr, are able to move up to high Galactic latitude. Moreover, their gamma-ray luminosities are weaker, and their spectra are significantly softer than those of younger gamma-ray pulsars in the Galactic plane. We use a Monte Carlo method to simulate the statistical properties of gamma-ray pulsars in the Galaxy as well as in the Gould Belt. We find that gamma-ray pulsars located at \b\ < 5° and |b| > 5degrees have very different properties. High Galactic latitude gamma-ray pulsars are dominated by mature pulsars with longer periods, weaker fluxes, and softer spectra. If the pulsar birth rates in the Galaxy and the Gould Belt are similar to10(-2) and similar to2 x 10(-5) yr(-1), respectively, there are 42 and 35 radio-quiet gamma-ray pulsars for \b\ < 5° and |b| > 5degrees, respectively. The number of radio-quiet gamma-ray pulsars from the GouldBelt are 2 and 13 for \b\ < 5° and |b| > 5degrees, respectively. We suggest that a good fraction of unidentified EGRET gamma-ray sources may be these radio-quiet gamma-ray pulsars. Furthermore, gamma-ray pulsars located at \b\ > 5degrees satisfy L-gamma proportional to L-sd(beta), whereas L-gamma proportional to L-sd(delta) for gamma-ray pulsars in the Galactic plane, where beta similar to 0.6 and delta similar to 0.3, respectively.