Thermal SZ effect in a magnetized IGM dominated by interacting DM
  decay/annihilation during dark ages
  During cosmic dawn, the thermal history of the universe is well studied, and
a study of this era can give us some of the most useful insight into the
universe before the recombination epoch. Its precise modeling and future
high-precision measurements will be a valuable tool for determining the thermal
history of the universe. In the present work, we study the thermal and
ionization history of IGM in the presence of decaying magnetic fields via
ambipolar and turbulent decay, Baryon-Dark matter (BDM) interaction, including
the DM decay/annihilation. The BDM interaction cross-sections considered are of
the form $\sigma=\sigma_0 v^{n}$, where $n=-2$ and $n=-4$. In this work, we
show that in the current scenario, the decay/annihilation of the DM particles
have a considerable impact on the temperature and ionization histories at low
redshift. With the addition of the concept of fractional interaction, which
states that if a fraction of the DM particles interacts with the baryons, the
temperature and ionization fraction of the baryons show a strong dependence on
the percentage of DM particles interacting with the baryons. We have also
studied the interesting consequences of the present scenario on the thermal
Sunyaev-Zeldovich (tSZ) effect. We show that the highest value of the absolute
value of the mean $y-$parameter in the current DM decay/annihilation scenario
is well within the values derived from experimental data such as PLANCK, FIRAS,
and PIXIE. Later we calculate the bound on the ordinary magnetic fields
originating from the Dark photons.
