Detection of a gamma-ray source in the Galactic Center consistent with extended emission from dark matter annihilation and concentrated astrophysical emission

Kevork N. Abazajian and Manoj Kaplinghat

Phys. Rev. D 86, 083511 – Published 8 October 2012; Erratum Phys. Rev. D 87, 129902 (2013)

Abstract

We show the existence of a statistically significant, robust detection of a gamma-ray source in the Milky Way Galactic Center that is consistent with a spatially extended signal using about 4 years of Fermi-LAT data. The gamma-ray flux is consistent with annihilation of dark matter particles with a thermal annihilation cross section if the spatial distribution of dark matter particles is similar to the predictions of dark matter only simulations. We find statistically significant detections of an extended source with gamma-ray spectrum that is consistent with dark matter particle masses of approximately 10 GeV to 1 TeV annihilating to $b \bar{b}$ quarks and masses approximately 10–30 GeV annihilating to $τ \bar{τ}$ leptons. However, a part of the allowed region in this interpretation is in conflict with constraints from Fermi observations of the Milky Way satellites. The biggest improvement over the fit including just the point sources is obtained for a 30 GeV dark matter particle annihilating to $b \bar{b}$ quarks. The gamma-ray intensity and spectrum are also well fit with emission from a millisecond pulsar population following a density profile like that of low-mass x-ray binaries observed in M31. The greatest goodness of fit of the extended emission is with spectra consistent with known astrophysical sources like millisecond pulsars in globular clusters or cosmic-ray bremsstrahlung on molecular gas. Therefore, we conclude that the bulk of the emission is likely from an unresolved or spatially extended astrophysical source. However, the interesting possibility of all or part of the extended emission being from dark matter annihilation cannot be excluded at present.

Received 31 July 2012

DOI:https://doi.org/10.1103/PhysRevD.86.083511

Erratum

Erratum: Detection of a gamma-ray source in the Galactic Center consistent with extended emission from dark matter annihilation and concentrated astrophysical emission [Phys. Rev. D 86, 083511 (2012)]

Kevork N. Abazajian and Manoj Kaplinghat

Phys. Rev. D 87, 129902 (2013)

Authors & Affiliations

Kevork N. Abazajian^* and Manoj Kaplinghat^†

Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697, USA

^*kevork@uci.edu
^†mkapling@uci.edu

Astrophysical and dark matter interpretations of extended gamma-ray emission from the Galactic Center

Kevork N. Abazajian, Nicolas Canac, Shunsaku Horiuchi, and Manoj Kaplinghat

Phys. Rev. D 90, 023526 (2014)

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Vol. 86, Iss. 8 — 15 October 2012

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Images

Figure 1
Shown in the top row are photon counts in four energy bins that have significant evidence for an extended source with a spectrum, morphology, and rate consistent with a 30 GeV mass WIMP annihilating to $b \bar{b}$ quarks in the $7 ° \times 7 °$ region about the GC. This row shows the 17 2FGL point sources in the ROI as circles. The second row shows the residuals for the fit to the region varying all the sources in the 2FGL catalog as well as the amplitudes of Galactic diffuse and isotropic diffuse models. The presence of an extended source and oversubtraction of the central point sources are visible here. The third row shows the best-fit model counts for 30 GeV WIMP annihilating to $b \bar{b}$ quarks. The fourth row is the residual emission for this model without subtracting the extended component. The fifth row contains the residuals when the extended component is also subtracted. The maps have been filtered with a Gaussian of width $σ = 0.3 °$ .Reuse & Permissions
Figure 2
Shown in the top row are photon counts in four energy bins that have significant evidence for an extended source with a spectrum, morphology, and rate consistent with a 100 GeV mass WIMP annihilating to $b \bar{b}$ quarks in the $7 ° \times 7 °$ region about the GC. The panels show fits and residuals in the same manner as Fig. 1, but for higher energies. The maps have been filtered with a Gaussian of width $σ = 0.3 °$ . The 17 point sources in the ROI are marked as circles in the top panels.Reuse & Permissions
Figure 3
Shown in the top row are the photon counts in four energy bins in the $7 ° \times 7 °$ region about the GC that have significant evidence for an extended source with a central morphology consistent a projected density-squared map with a central density profile index $γ = 1.3$ . This could be consistent with a concentrated population of unresolved points sources as discussed in Sec. 5. The extended source is best fit with a log-parabola spectrum. The panels show fits and residuals in the same manner as Fig. 1. The maps have been filtered with a Gaussian of width $σ = 0.3 °$ . The 17 point sources in the ROI are marked as circles in the top panels.Reuse & Permissions
Figure 4
Shown are the parameters of particle dark matter mass $m_{χ}$ and cross section $⟨ σ v ⟩$ for annihilation to $b \bar{b}$ quarks consistent with the extended gamma-ray source in the GC at 68% C.L. (dark pink) for a dark matter density profile with central slope $γ = 1.2$ [cf. Eq. (2.1)], our best-fit spatial model. The red line is the case of $ρ_{⊙} = 0.3 GeV {cm}^{- 3}$ . The diagonally hatched region is approximately where the $2 Δ \ln L$ significance drops below $\approx 5 σ$ . The light pink region shows the extension of the consistency region for $γ = 1.3$ , with the vertically hatched region corresponding to approximately where the $2 Δ \ln L$ significance drops below $\approx 5 σ$ . The region above the solid line indicates the parameters excluded at 95% C.L. by stacked dwarf analyses [10]. The region above the dashed line indicates the parameters excluded at 95% C.L. by HESS observations of the GC [14]. We have assumed here that all of the extended emission is due to dark matter annihilation. If only part of it is due to dark matter, then the required cross section should be lower.Reuse & Permissions
Figure 5
Shown are the parameters of particle dark matter mass $m_{χ}$ and cross section $⟨ σ v ⟩$ for annihilation to $τ^{+} τ^{-}$ leptons consistent with the extended gamma-ray source in the GC at 68% C.L. for a central density profile of $γ = 1.2$ (the best-fit model, in dark pink) and $γ = 1.3$ (light pink). The red line is for the case of $ρ_{⊙} = 0.3 GeV {cm}^{- 3}$ . The diagonally and vertically hatched regions are approximately where the $2 Δ \ln L$ significance drops below $\approx 5 σ$ for the $γ = 1.2$ and $γ = 1.3$ cases, respectively. The region above the solid line indicates the parameters excluded at 95% C.L. by stacked dwarf analyses [10].Reuse & Permissions

Physical Review D

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