= Solution
<annihilation> can produce <gamma rays>, charged <antiparticles> and <neutrinos>, directly or through decay and <hadronization> of the primary products. For self-conjugate <dark matter> of <mass> $m_\chi$, the <annihilation> rate per unit volume is $\langle\sigma v\rangle\rho_\chi^2/(2m_\chi^2)$. For a <photon> yield $dN_\gamma/dE$, the optically thin flux from a chosen solid angle is
$$
\frac{d\Phi_\gamma}{dE}=\frac{\langle\sigma v\rangle}{8\pi m_\chi^2}\frac{dN_\gamma}{dE}\,
\underbrace{\int_{\Delta\Omega}d\Omega\int_{\rm los}\rho_\chi^2\,dl}_{J}.
$$
Use consistent mass-energy units. The factor $1/2$ assumes identical self-conjugate particles; distinct particle-antiparticle populations require their separate <number densities>. A gamma-ray continuum with an endpoint near the particle <mass> is generic for many channels, whereas a narrow line from $\chi\chi\to\gamma\gamma$ or $\gamma Z$ would be especially distinctive but often loop suppressed. <dwarf spheroidal galaxies> offer high dark-matter content with limited conventional emission; the <Galactic centre> has a potentially larger signal and much more complicated foregrounds.
Charged <Positrons> and <antiprotons> are redistributed by <magnetic fields> and lose <energy>, so their <radiation spectrum> depend on propagation and cannot usually point directly to the source. <annihilation> <electrons> can also produce synchrotron and inverse-Compton radiation. <dark matter> captured in the Sun could produce escaping high-energy <neutrinos>, with the signal depending on capture, <annihilation> equilibrium and particle interactions. Early <annihilation> <energy> injection can alter recombination and <cosmic microwave background> anisotropies.
\b[A persuasive interpretation joins particle-like spectral structure with a consistent density-dependent morphology and other channels.] Pulsars, cosmic-ray interactions and unresolved sources can imitate continuum excesses. Density-profile uncertainties, substructure and velocity-dependent <annihilation> modify the predicted signal; a lack of a detectable line does not exclude all annihilating <dark matter>.
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