Strong 21-cm fluctuations and anisotropy due to the line-of-sight effect of radio galaxies at cosmic dawn

Understand

The reported detection of the global 21-cm signal by the EDGES collaboration is significantly stronger than standard astrophysical predictions.

• One possible explanation is an early radio excess above the cosmic microwave background.
• Such a radio background could have been produced by high redshift galaxies, if they were especially efficient in producing low-frequency synchrotron radiation.
• We have previously studied the effects of such an inhomogeneous radio background on the 21-cm signal; however, we made a simplifying assumption of isotropy of the background seen by each hydrogen cloud.