Signatures of clumpy dark matter in the global 21 cm background signal

Abstract

We examine the extent to which the self-annihilation of supersymmetric neutralino dark matter, as well as light dark matter, influences the rate of heating, ionisation and Lyman-α pumping of interstellar hydrogen and helium and the extent to which this is manifested in the 21 cm global background signal. We fully consider the enhancements to the annihilation rate from DM halos and substructures within them. We find that the influence of such structures can result in significant changes in the differential brightness temperature, δT b . The changes at redsfhits z < 25 are likely to be undetectable due to the presence of the astrophysical signal; however, in the most favourable cases, deviations in δT b , relative to its value in the absence of self-annihilating DM, of up to ≃ 20 mK at z = 30 can occur. Thus we conclude that, in order to exclude these models, experiments measuring the global 21 cm signal, such as EDGES and CORE, will need to reduce the systematics at 50 MHz to below 20 mK.PACS numbers: 95.35+d

Energy injection and absorption in the cosmic dark ages

“…This is appropriate at high redshift, when density fluctuations are small and perturbative, and conservative in all cases; it allows a very robust and precise constraint, since the cosmological density of the DM is constrained at the percent level. However, there has been considerable interest in the effects of DM annihilation/decay at lower redshifts (z 30) where there might be measurable effects on the 21 cm line of hydrogen [17][18][19][20][21][22], or where the annihilation byproducts might help reionize the universe [23][24][25][26][27].…”

Constraints on the basic parameters of dark matter using the Planck data

“…1 in Ref. [15]). For DM halo mass 10 6 M ⊙ , the differences of ∼ 5 orders of magnitude differences are present at z ∼ 20 compared with the DM smooth distribution.…”

“…In the Ref. [15], the authors discussed the effects on the 'boost factor' for the different values of the smallest DM halos. They found that there are differences of ∼ 2 orders of magnitude of the 'boost factor' for DM halo mass 10 −12 M ⊙ and 10 −4 M ⊙ at z ∼ 50 (upper panel of Fig.…”

“…We use the power law form of the mass function ∼ M 1.95 for the subhalos [12]. The total boost factor of DM halos including the subhalos is [15] …”

“…For the boost factor B(z) we followed the Ref. [15] and used the form as (5) where dn/dM is the mass function of DM halos and we use the Press-Schechters formalism for our calculations [16]. For the DM halos, we use the NFW (NavarroFrenk-White) density profile.…”