On the gamma-ray emission from the core of the Sagittarius dwarf galaxy

• We use Fermi-LAT data to analyse the faint gamma-ray source located at the centre of the Sagittarius (Sgr) dwarf spheroidal galaxy. In the 4FGL-DR3 catalogue, this source is associated with the globular cluster, M54. We investigate the spectral energy distribution and spatial extension of this source, with the goal of testing two hypotheses: (1) the emission is due to millisecond pulsars within M54, or (2) the emission is due to annihilating dark matter from the Sgr halo. For the pulsar interpretation, we consider a two-component model which describes both the lower-energy magnetospheric emission and possible high-energy emission arising from inverse Compton scattering. We find that this source has a point-like morphology at low energies, consistent with magnetospheric emission, and find no evidence for a higher-energy component. For the dark matter interpretation, we find the signal favours a dark matter mass of m(chi)= 29.6 +/- 5.8 GeV and an annihilation cross section of sv = (2. 1 +/- 0.59) x10(-26) cm(3) s(-1) for the b b channel (or m(chi)= 8.3 +/- 3.8 GeV and sv = (0.90 +/- 0.25) x10-26 cm(3) s(-1) for the tau(+) tau(-) channel), when adopting a J -factor of J = 1019.6 GeV2 cm(-5). This parameter space is consistent with gamma-ray constraints from other dwarf galaxies and with dark matter interpretations of the Galactic Centre Gamma-Ray Excess.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

astroparticle physics - globular clusters - galaxies

dwarf - dark matter - gamma-rays

general

astroparticle physics

globular clusters

galaxies: dwarf

dark matter

gamma-rays: general.

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