Abstract
Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(-26) cm3 s(-1) at 5 GeV to about 5×10(-23) cm3 s(-1) at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (∼3×10(-26) cm3 s(-1) for a purely s-wave cross section), without assuming additional boost factors.
Highlights
It is well established that baryons contribute only about 20% of the mass density of matter in the universe [1]
For large constant density cores, this results in a larger J-factor if the pair annihilation flux is integrated over a solid angle larger than that encompassing half the stellar luminosity
The Dark Matter (DM) mass distribution as a function of the radius from the center of the dwarf is modeled as an Navarro-Frenk-White profile given by ρ(r) = 0.08Vm2axrs/(Gr(r + rs)2), where Vmax is the maximum circular velocity possible for the dark matter halo
Summary
It is well established that baryons contribute only about 20% of the mass density of matter in the universe [1]. For large constant density cores (comparable to or larger than the dSph halflight radius), this results in a larger J-factor if the pair annihilation flux is integrated over a solid angle larger than that encompassing half the stellar luminosity This is due to the fact that flux is dominated by annihilations in the outer parts for 1/r and shallower dark matter density profiles. The DM mass distribution as a function of the radius from the center of the dwarf is modeled as an Navarro-Frenk-White profile given by ρ(r) = 0.08Vm2axrs/(Gr(r + rs)2), where Vmax is the maximum circular velocity possible for the dark matter halo For this profile, the J-factor in units of GeV2cm−5. The posterior distribution as well as the likelihood function for J are well described by a logNormal function, which is used in order to include the uncertainty on J in the confidence interval calculation, as described
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