Constraints on primordial magnetic fields in the light of ARCADE-2 and EDGES observations

The 21-cm signal, due to the hyperfine transition in the neutral hydrogen atom, appears to be a treasure trove to study physics in the cosmic dawn era. The presence of an exotic physical process can inject energy into the intergalactic medium (IGM) and heat up the gas. Subsequently, it can modify the absorption amplitude in the global 21-cm signal during cosmic dawn. The absorption feature in the 21-cm signal can provide a robust bound on such a process of energy injection. Recently, the EDGES observation reported such an absorption signal in the redshift range 15-20. It is nearly two times larger than theoretical predictions based on the LCDM model. In order to explain the observation, one may require to increase the background radiation temperature above CMB or decrease the gas temperature. ARCADE-2 observation detected extra-galactic excess radio radiation in the frequency range of 3-90 GHz. The primordial magnetic fields (PMFs) can inject energy into IGM by ambipolar diffusion and turbulent decay. In the presence of decaying PMFs, the 21-cm signal can modify due to the heating of the gas. We will discuss the constraints on PMFs in the light of the EDGES low-band and ARCADE-2 observations.