We derive the evolution of the energy deposition in the intergalactic medium (IGM) by dark matter (DM) decays/annihilations for both sterile neutrinos and light dark matter (LDM) particles. At z > 200 sterile neutrinos transfer a fraction fabs ~ 0.5 of their rest mass energy into the IGM; at lower redshifts this fraction becomes <~0.3 depending on the particle mass. The LDM particles can decay or annihilate. In both the cases fabs ~ 0.4-0.9 at high (>300) redshift, dropping to ~0.1 below z = 100. These results indicate that the impact of DM decays/annihilations on the IGM thermal and ionization history is less important than previously thought. We find that sterile neutrinos (LDM) decays are able to increase the IGM temperature by z = 5 at most up to 4K (100K), about 50-200 times less than predicted by estimates based on the assumption of complete energy transfer to the gas.
Intergalactic medium heating by dark matter
FERRARA, ANDREA
2007
Abstract
We derive the evolution of the energy deposition in the intergalactic medium (IGM) by dark matter (DM) decays/annihilations for both sterile neutrinos and light dark matter (LDM) particles. At z > 200 sterile neutrinos transfer a fraction fabs ~ 0.5 of their rest mass energy into the IGM; at lower redshifts this fraction becomes <~0.3 depending on the particle mass. The LDM particles can decay or annihilate. In both the cases fabs ~ 0.4-0.9 at high (>300) redshift, dropping to ~0.1 below z = 100. These results indicate that the impact of DM decays/annihilations on the IGM thermal and ionization history is less important than previously thought. We find that sterile neutrinos (LDM) decays are able to increase the IGM temperature by z = 5 at most up to 4K (100K), about 50-200 times less than predicted by estimates based on the assumption of complete energy transfer to the gas.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
