Populating the Galaxy with pulsars -- II. Galactic dynamics

TL;DR

This paper models the distribution and velocities of pulsars in the Galaxy, examining how different factors influence their spatial and velocity characteristics, and predicting populations including rare systems like millisecond pulsars with black hole companions.

Contribution

It introduces a comprehensive synthetic population model of pulsars, analyzing the effects of Galactic potential, birth distributions, and velocity kicks, and explores the formation of unique pulsar systems.

Findings

Isolated pulsars have greater scale heights than binary pulsars.

Binary pulsars' scale heights are comparable to isolated pulsars when low-mass star ablation is considered.

Some double neutron star systems have velocities similar to the Sun.

Abstract

We produce synthetic populations of pulsars within our Galaxy and calculate the resulting scale heights as well as the radial and space velocity distributions of the pulsars. Results are presented for isolated pulsars, binary pulsars and millisecond pulsars. We also test the robustness of the outcomes to variations in the assumed form of the Galactic potential, the birth distribution of binary positions, and the strength of the velocity kick given to neutron stars at birth. We find that isolated pulsars have a greater scale height than binary pulsars. This is also true when restricted to millisecond pulsars unless we allow for low-mass stars to be ablated by radiation from their pulsar companion in which case the isolated and binary scale heights are comparable. Double neutron stars are found to have a large variety of space velocities, in particular, some systems have speeds similar to the Sun. We look in detail at the predicted Galactic population of millisecond pulsars with black hole companions, including their formation pathways, and show where the short-period systems reside in the Galaxy. Some of our population predictions are compared in a limited way to observations but the full potential of this aspect will be realised in the near future when we complete our population synthesis code with the selection effects component.