Pulsar motions in our Galaxy

Abstract

Pulsar motions in our Galaxy from their birth until age 2 Gyr are studied statistically via Monte Carlo simulation of 2 × 105 pulsars with the best available representation of the Galactic potential. We find that the distribution of heights above the Galactic plane for pulsars with characteristic ages less than about 8 Myr could be well fitted by a Gaussian function. For older pulsars, an extra exponential function is necessary to fit the distribution. The scaleheight of the Gaussian component increases linearly with time until about 40 Myr. The height distribution becomes stabilized after about 200 Myr. These results are not sensitive to initial height or radial distributions. Taking the relationship between the initial velocity and height distribution, we found from the latest pulsar catalogue that the height distribution of pulsars younger than 1 Myr directly implies a mean initial velocity of 280 ± 96 km s-1. Comparison of a simulated sample of pulsars with the currently available millisecond pulsars shows that their 1D initial velocity dispersion should be most probably 60 ± 10 km s -1.