Baryon-Dark matter interaction in presence of magnetic fields in light of EDGES signal

Abstract

We have shown that in presence of a cosmic magnetic field the bounds on baryon dark matter cross-section ($\hat{\sigma }$), dark-matter mass ($m_d$) and values of the magnetic field ($B_0$) can strongly influence each other. This requires to rework the bounds on $\hat{\sigma }$, $m_d$ and $B_0$ which can explain the observed absorption signal by EDGES collaboration. The upper limit on the magnetic field strength can modify in presence of baryon-dark matter interaction cross-section. In the presence of a strong magnetic field, a large baryon-dark matter interaction cross-section is required to balance magnetic heating of gas to explain the EDGES signal as compared to a weak magnetic field. Subsequently, the strong magnetic-fields can even erase the 21 cm signal--this gives an upper bound on the strength of magnetic-fields, dark-matter mass and baryon-dark matter cross-section. In the special case when $\hat{\sigma }$=0, one can recover the bound on magnetic field strength calculated in [1]. In this work we find that the allowed range of the primordial magnetic field can increase by three orders of magnitude in comparison with [1]. We get upper bound on the magnetic field strength: $3.48\times 10^{-6}$ G for the dark matter mass $\lesssim 10^{-2}$ GeV.

9 pages and 6 figures