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Limits on Supersymmetric Dark Matter From EGRET Observations of the Galactic Center Region

Dan Hooper, Brenda Dingus

TL;DR

This work addresses whether gamma rays from neutralino annihilation in the Galactic center can constrain supersymmetric dark matter under different Galactic halo profiles. The authors develop an improved EGRET analysis using an energy-dependent point-spread function and an unbinned maximum-likelihood approach, validating it with known pulsars before applying it to the GC to obtain 95% CL upper limits on the point-source flux. They compute predicted gamma-ray fluxes for a seven-parameter MSSM subset under accelerator bounds and relic-density constraints $0.05<Ωχ h^2<0.2$ for cuspy halo models (NFW and Moore), finding that very cuspy halos exclude a large portion of viable models; GLAST is forecast to dramatically improve sensitivity and test additional scenarios. The results link particle properties to the central dark matter density, emphasizing that indirect detection prospects hinge on the inner halo structure and will be refined by next-generation gamma-ray observatories.

Abstract

In most supersymmetic models, neutralino dark matter particles are predicted to accumulate in the Galactic center and annihilate generating, among other products, gamma rays. The EGRET experiment has made observations in this region, and is sensitive to gamma rays from 30 MeV to $\sim$30 GeV. We have used an improved point source analysis including an energy dependent point spread function and an unbinned maximum likelihood technique, which has allowed us to significantly lower the limits on gamma ray flux from the Galactic center. We find that the present EGRET data can limit many supersymmetric models if the density of the Galactic dark matter halo is cuspy or spiked toward the Galactic center. We also discuss the ability of GLAST to test these models.

Limits on Supersymmetric Dark Matter From EGRET Observations of the Galactic Center Region

TL;DR

This work addresses whether gamma rays from neutralino annihilation in the Galactic center can constrain supersymmetric dark matter under different Galactic halo profiles. The authors develop an improved EGRET analysis using an energy-dependent point-spread function and an unbinned maximum-likelihood approach, validating it with known pulsars before applying it to the GC to obtain 95% CL upper limits on the point-source flux. They compute predicted gamma-ray fluxes for a seven-parameter MSSM subset under accelerator bounds and relic-density constraints for cuspy halo models (NFW and Moore), finding that very cuspy halos exclude a large portion of viable models; GLAST is forecast to dramatically improve sensitivity and test additional scenarios. The results link particle properties to the central dark matter density, emphasizing that indirect detection prospects hinge on the inner halo structure and will be refined by next-generation gamma-ray observatories.

Abstract

In most supersymmetic models, neutralino dark matter particles are predicted to accumulate in the Galactic center and annihilate generating, among other products, gamma rays. The EGRET experiment has made observations in this region, and is sensitive to gamma rays from 30 MeV to 30 GeV. We have used an improved point source analysis including an energy dependent point spread function and an unbinned maximum likelihood technique, which has allowed us to significantly lower the limits on gamma ray flux from the Galactic center. We find that the present EGRET data can limit many supersymmetric models if the density of the Galactic dark matter halo is cuspy or spiked toward the Galactic center. We also discuss the ability of GLAST to test these models.

Paper Structure

This paper contains 4 sections, 3 figures.

Table of Contents

  1. Introduction
  2. EGRET Point Source Location Analysis
  3. Calculating The Gamma Ray Flux from the Galactic Center
  4. Conclusions

Figures (3)

  • Figure 1: Unbinned maximum likelihood point source analysis of the Galactic center region. 50, 68, 95, 99 and 99.9% confidence intervals on the point source position are shown. Note that the Galactic center is excluded beyond the 99.9% confidence level as the location of the source. The 95% confidence contour of the 3EG catalog position is shown as a circle for comparison. Also shown are all gamma rays above 5 GeV.
  • Figure 2: SUSY model predicted fluxes for a Moore et. al. halo profile. Also shown are the 95% confidence upper limit of EGRET (solid line) and the expected GLAST sensitivity (dashed line). Blue circles represent models with an LSP which is more than 95% higgsino, red stars represent models with an LSP which is more than 95% gaugino and black x's are models with mixed neutralinos.
  • Figure 3: SUSY model predicted fluxes for a NFW halo profile. Also shown are the 95% confidence upper limit of EGRET (solid line) and the expected GLAST sensitivity (dashed line). Blue circles represent models with an LSP which is more than 95% higgsino, red stars represent models with an LSP which is more than 95% gaugino and black x's are models with mixed neutralinos.