Reionization

Today in IPM/Tehran/There is a lecture talk about the law frequency radio astronomy.

In the conclusion part, the lecturer state that one of the applications of law frequency radio astronomy is detecting objects in reionization era.

Now what is reionization era.

Let me do a little job to describe it.

In the history of universe two major phase transition occurred for hydrogen.

First of it was in the time of recombination/redshift z~1100 / 400,000years after big bang when the rate of combination of electron to protons became higher than the ionization of hydrogen atom so in consequence of this the hydrogen atoms formed and the universe become transparent for photons.This is the last scattering surface and the photons coming from this redshift are the cosmic microwave background radiation photons.

The second phase transition occurred in reionization era, 150 million to 1 billion year after big band/redshift of 20 to 6/ because of formation of structures high energy became free and the universe /the intergalactic medium /changes it phase and from neutral become ionized and transformed to plasma.In this case the protons and electrons which are not bound can not capture the photons so they become transparent to it.

There are different techniques to found out about this era,which in future posts I will introduce them first of all for my self like.

Techniques are:

Quasars and the Gunn-Peterson trough

CMB anisotropy and polarization

21-cm line