Dark matter profiles and annihilation in dwarf spheroidal galaxies: prospectives for present and future γ-ray observatories - I. The classical dwarf spheroidal galaxies

摘要: Due to their large dynamical mass-to-light ratios, dwarf spheroidal galaxies (dSphs) are promising targets for the indirect detection of dark matter (DM) in γ-rays. We examine detectability by present and future γ-ray observatories. The key innovative features our analysis as follows: (i) we take into account angular size dSphs; while nearby objects have higher flux, larger extent can make them less attractive background-dominated instruments; (ii) derive DM profiles astrophysical J-factor (which parametrizes expected independently choice particle model) classical dSphs directly from photometric kinematic data. assume very little about profile, modelling this a smooth split-power-law distribution, with without subclumps; (iii) use Markov chain Monte Carlo technique marginalize over unknown parameters determine sensitivity derived J-factors both model measurement uncertainties; (iv) simulated demonstrate that determinations recover correct solution within quoted uncertainties. Our findings subclumps do not usefully boost signal; atmospheric Cherenkov telescopes ∼20 kpc cored haloes be up ∼50 times worse than when estimated assuming point-like. Even satellite-borne Fermi-Large Area Telescope (Fermi-LAT), is significantly degraded on relevant scales long exposures; hence, it vital consider selecting targets; no profile has been ruled out current data, but using prior inner cusp slope 0 ≤γprior≤ 1 provides estimates accurate factor few if an appropriate scale chosen; best constrained at critical integration angle αc= 2rh/d (where rh half-light radius d distance dwarf) estimate corresponding observatories; (v) ‘classical’ grouped three categories: well (Ursa Minor, Sculptor Draco), (Carina, Fornax Leo I), poorly (Sextans II); (vi) observations Fermi-LAT integrated mission lifetime more planned Array mass ≲ 700 GeV. However, even will sufficient signal dwarfs detect ‘vanilla’ Minimal Supersymmetric Standard Model. Both Galactic Centre ‘ultrafaint’ likely better considered work.