Detecting pulsars in the Galactic centre

TL;DR

This paper analyzes the challenges in detecting pulsars near the Galactic center, demonstrating current survey limitations and proposing optimal frequencies for future observations with advanced telescopes like the SKA.

Contribution

It provides a detailed assessment of the detectability of pulsars in the Galactic center considering absorption and scattering, and suggests optimal frequencies for future surveys.

Findings

Current surveys are insufficient to detect GC pulsars due to absorption and scattering.

Future surveys at 9-13 GHz can significantly improve detection prospects.

SKA will be capable of probing a large portion of the GC pulsar population.

Abstract

Although high-sensitivity surveys have revealed a number of highly dispersed pulsars in the inner Galaxy, none have so far been found in the Galactic centre (GC) region, which we define to be within a projected distance of 1~pc from Sgr~A*. This null result is surprising given that several independent lines of evidence predict a sizable population of neutron stars in the region. Here, we present a detailed analysis of both the canonical and millisecond pulsar populations in the GC and consider free-free absorption and multi-path scattering to be the two main sources of flux density mitigation. We demonstrate that the sensitivity limits of previous surveys are not sufficient to detect GC pulsar population, and investigate the optimum observing frequency for future surveys. Depending on the degree of scattering and free-free absorption in the GC, current surveys constrain the size of the potentially observable population (i.e.~those beaming towards us) to be up to 52 canonical pulsars and 10000 millisecond pulsars. We find that the optimum frequency for future surveys is in the range of 9--13~GHz. We also predict that future deeper surveys with the Square Kilometer array will probe a significant portion of the existing radio pulsar population in the GC.