Millisecond pulsar origin of the Galactic center excess and extended gamma-ray emission from Andromeda - a closer look

Understand

A new measurement of a spatially extended gamma-ray signal from the center of the Andromeda galaxy (M31) has been recently published by the Fermi-LAT collaboration, reporting that the emission broadly resembles the so-called Galactic center excess (GCE) of the Milky Way (MW).

• At the same time, evidence is accumulating on a millisecond pulsar (MSPs) origin for the GCE.
• These elements prompt us to compare the mentioned observations with what is, perhaps, the simplest model for an MSP population, solely obtained by rescaling of the MSP luminosity function determined in the local MW disk via the respective stellar mass of the systems.
• It is remarkable that without free fitting parameters, this model can account for both the energetics and the morphology of the GCE within uncertainties.