The International Gamma-Ray Astrophysics Laboratory ( INTEGRAL ) satellite has yielded unprecedented measurements of the soft gamma-ray spectrum of our Galaxy .
Here we use those measurements to set constraints on dark matter ( DM ) that decays or annihilates into photons with energies E \approx 0.02 - 2 MeV .
First , we revisit the constraints on decaying and annihilating particle DM .
For DM decaying to two photons , we find that previous limits were overstated by roughly an order of magnitude .
Our new , conservative analysis finds that the DM lifetime must satisfy \tau \gtrsim 10 ^ { 27 } { s } \times ( m _ { \chi } / MeV ) ^ { -1 } for DM masses m _ { \chi } = 0.054 - 3.6 MeV .
For MeV-scale DM that annihilates into photons INTEGRAL sets the strongest constraints to date , whereas for annihilations to electron-positron pairs , INTEGRAL only improves upon current limits when assuming p -wave annihilation .
Second , we target ultralight primordial black holes ( PBHs ) through their Hawking radiation .
This makes them appear as decaying DM with a photon spectrum peaking at E \approx 5 / ( 8 \pi GM _ { PBH } ) , for a PBH of mass M _ { PBH } .
We use the INTEGRAL data to demonstrate that PBHs with masses less than 2 \times 10 ^ { 17 } g can not comprise all of the DM , setting the tightest bound to date on ultralight PBHs .