  A one dimensional radiative transfer code is developed to track the
ionization and heating pattern around the first miniquasars and Population III
stars. The code follows the evolution of the ionization of the species of
hydrogen and helium and the intergalactic medium temperature profiles as a
function of redshift. The radiative transfer calculations show that the
ionization signature of the first miniquasars and stars is very similar yet the
heating pattern around the two is very different. Furthermore, the first
massive miniquasars (~>10^5 M_{sun}) do produce large ionized bubbles around
them, which can potentially be imaged directly using future radio telescopes.
It is also shown that the ionized bubbles not only stay ionized for
considerable time after the switching off of the source, but continue to expand
for a short while due to secondary collisions prompted by the X-ray part of
their spectra. Varying spectral shapes also produced sizable variations in
ionized fraction and temperature profile. We also compare the radiative
transfer results with the analytical approximation usually adopted for heating
by miniquasars and find that, because of the inadequate treatment of the He
species, the analytical approach leads to an underestimation of the temperature
in the outer radii by a factor ~5. Population III stars - with masses in the
range of 10 - 1000 M_{sun} and modelled as blackbodies at a temperature of
50000 K - are found to be efficient in ionizing their surroundings.
Observational effects on the 21 cm brightness temperature, the thermal and
kinetic Sunyaev-Ze'ldovich effects, are also studied in the context of the
upcoming radio and microwave telescopes like LOFAR and SPT.
