Radio sensitivity to a new population of millisecond pulsars in the Sagittarius Dwarf Spheroidal Galaxy

TL;DR

This study assesses the detectability of millisecond pulsars in the Sagittarius dwarf galaxy using radio surveys, highlighting SKA's superior sensitivity and potential to confirm gamma-ray excess origins.

Contribution

It introduces a phenomenological model to estimate MSP detection prospects in Sgr dSph with current and future radio telescopes, emphasizing SKA's capabilities.

Findings

SKA can identify approximately 9 MSPs in Sgr dSph with two hours of observation.

Detecting at least six MSPs with SKA can confirm the gamma-ray excess origin at 99.7% confidence.

A two-hour MeerKAT observation can detect one MSP in the Sgr dSph.

Abstract

Observations with the Fermi Gamma-Ray Space Telescope reveal an excess of extended gamma-ray emission likely caused by an undiscovered population of millisecond pulsars (MSPs) in the core of the Sagittarius dwarf spheroidal galaxy (Sgr dSph). However, additional evidence, such as multi-wavelength searches, is necessary to confirm this theory. A significant discovery could be made if radio pulsations from individual MSPs in the Sgr dSph are detected. In this study, we investigate the possibility of detecting MSPs in the Sgr dSph with present and upcoming radio surveys using a phenomenological model based on the observed luminosity function of MSPs in the Milky Way's globular clusters. Our findings suggest that the Square Kilometer Array (SKA) is the most sensitive instrument for detecting these objects. We demonstrate that to observe one MSP with MeerKAT, we would need to perform a pointing observation of the core region of the Sgr dSph for about two hours. In this same observation time, SKA can identify $9^{+5}_{-3}$ MSPs in the entire system. Based on the distance of the Sgr dSph galaxy and our dispersion measure distance estimate, we find it possible to differentiate between MSPs belonging to the Sgr dSph and those of the Galactic disk and bulge. Furthermore, the MSPs hypothesis for the Sgr dSph gamma-ray excess could be confirmed at the 99.7\% confidence level by detecting at least six MSPs in a two-hour SKA observation of the Sgr dSph.