Known radio pulsars do not contribute to the Galactic Center gamma-ray excess

Abstract

Observations using the Fermi Large Area Telescope (Fermi-LAT) have found a significant γ-ray excess surrounding the center of the Milky Way (GC). One possible interpretation of this excess invokes γ-ray emission from an undiscovered population of either young or recycled pulsars densely clustered throughout the inner kiloparsec of the Milky Way. While these systems, by construction, have individual fluxes that lie below the point source sensitivity of the Fermi-LAT, they may already be observed in multiwavelength observations. Notably the Australia Telescope National Facility (ATNF) catalog of radio pulsars includes 270 sources observed in the inner 10 • around the GC. We calculate the γ-ray emission observed from these 270 sources and obtain three key results: (1) point source searches in the GC region produce a plethora of highly significant γ-ray "hotspots", compared to searches far from the Galactic plane, (2) there is no statistical correlation between the positions of these γ-ray hotspots and the locations of ATNF pulsars, and (3) the spectrum of the most statistically significant γ-ray hotspots is substantially softer than the spectrum of the GC γ-ray excess. These results place strong constraints on models where young pulsars produce the majority of the γ-ray excess, and disfavors some models where milli-second pulsars produce the γ-ray excess.

Low mass X-ray binaries in the Inner Galaxy: implications for millisecond pulsars and the GeV excess

“…Stacking this list of sources, we find that the total gamma-ray luminosity from this collection of globular clusters is given by L γ = 1.39 +0.04 −0.05 × 10 36 erg/s, >0.1 GeV. After applying a mirrored sky location test [38,68], we confirm that our false detection rate is expected to be small, and that spurious detections are unlikely to significantly impact this determination. 2 [67], and stellar encounter rates of the 22 globular clusters in the Milky Way with stellar encounter rates of Γ e > 0.5, as calculated in Ref.…”

A review of indirect searches for particle dark matter

“…There is not yet consensus on the size of the contribution of MSPs or other sources to the diffuse emission in the Inner Galaxy [129][130][131][132][133]. While analyses sensitive to sub-threshold sources suggest that such sources could provide an important contribution to the emission [134,135], curiously it does not appear that the sub-threshold sources are associated with known radio pulsars [136].…”

Dark matter implications of the WMAP-Planck Haze

“…In addition to the DM interpretation, other explanations considered for this excess include a population of unresolved gamma-ray millisecond pulsars (MSPs) [9,11,[13][14][15][16][17] and gamma rays from CRs injected in bursts near the GC [18][19][20]. Recent results suggest that the majority of the excess emission arises from a population of unresolved sources such as MSPs [21,22], however those sources have not been identified in multi-wavelength studies (see, e.g., [23]), and there remains some debate in the community, leaving open the exciting possibility that the excess represents a detection of DM annihilation.…”