Natural explanation for 21cm absorption signals via axion-induced
  cooling
  The EDGES Collaboration has reported an anomalously strong 21cm absorption
feature corresponding to the era of first star formation, which may indirectly
betray the influence of dark matter during this epoch. We demonstrate that, by
virtue of the ability to mediate cooling processes whilst in the condensed
phase, a small amount of axion dark matter can explain these observations
within the context of standard models of axions and axion-like-particles. The
EDGES best-fit result favours an axion-like-particles mass in the (10, 450) meV
range, which can be compressed for the QCD axion to (100, 450) meV in the
absence of fine tuning. Future experiments and large scale surveys,
particularly the International Axion Observatory (IAXO) and EUCLID, should have
the capability to directly test this scenario.
