Population syntheses of millisecond pulsars from the Galactic Disk and Bulge

TL;DR

This study models the population of millisecond pulsars in the Milky Way, predicting their numbers and properties in the disk, globular clusters, and the bulge, and compares these with Fermi gamma-ray observations.

Contribution

It introduces a comprehensive population synthesis model for radio and gamma-ray MSPs, testing different high-energy emission geometries and matching observed distributions.

Findings

Predicted ~170 MSPs detectable by Fermi in the next decade.

Simulated MSP populations align with current Fermi detections.

Estimated ~11,000 MSPs in the Galactic Bulge to explain gamma-ray excess.

Abstract

We present the results of a population synthesis of radio and gamma-ray millisecond pulsars (MSPs) from the Galactic Disk (GD). Using 92 radio millisecond pulsars detected in 13 radio surveys and 54 Fermi MSPs detected as point sources in the first point source catalog, we establish six free parameters corresponding to the overall factor and the exponents of the period and period derivative dependence for each of the radio and gamma-ray empirical luminosity models. We test three high-energy emission models described by the two pole caustic Slot Gap, Outer Gap, and Pair Starved Polar Cap geometries. The simulated distributions of pulsar properties adequately describe the distributions of detected MSPs from the GD. We explore the gamma-ray emission from groups of MSPs in globular clusters and in the Galactic Bulge. The simulation predicts reasonable numbers of Fermi MSPs detected in the other point source catalogs and anticipates a bright future for Fermi observations of MSPs, expecting a total of ~ 170 MSP detections from the GD within ten years. Our numbers of simulated MSPs in globular clusters are in agreement with those derived from Fermi detections. The simulation predicts about 11,000 MSPs in the Galactic Bulge are required to explain the gamma-ray Galactic Center Excess.