Dark matter revealed by the first stars?

The cosmic radio spectrum is expected to show a strong absorption

signal around redshift 20 that corresponds to the rise of the first

stars; specifically, the stellar radiation turns on 21-cm absorption

by atomic hydrogen. The EDGES global 21-cm experiment has detected the

first such signal, finding a stronger absorption than the maximum

expected. This absorption can be explained by invoking excess cooling

of the cosmic gas induced by an interaction with dark matter. This

would have far reaching consequences, including an upper limit on the

mass of dark matter particles that conflicts with the expectations for

WIMPs. Specific particle physics models are highly constrained, but

observations will decide. In particular, we predict that 21-cm

fluctuations at cosmic dawn could be much larger than

previously expected, exhibiting a specific signature of dark matter.