Tirthankar Roy Choudhury

Cosmological Reionization:

In the framework of the hot big bang model, our Universe is expected to become almost neutral around 400,000 years after the big bang. On the other hand, we know from observations of quasar absorption spectra that the same Universe has become highly ionized by the time it is one Gigayear old. This implies that the Universe must have been "reionized" sometime in between. As per our current understanding, the reionization of the Universe is driven by radiation from first luminous sources (galaxies/stars). Studying reionization will thus tell us how the first stars formed and how different they were from stars we see around us. In addition, reionization is extremely important for studying cosmology in general as the details of it affect the determination of cosmological parameters from observations. I have been involved in theoretical modeling of the process of reionization and comparing these models with different observations. I am also interested in developing numerical simulations to generate realistic maps of HI 21cm emission arising from the hyperfine transition of neutral hydrogen, that might be observed with current and upcoming radio telescopes such as the GMRT, the Low-Frequency Array (LOFAR) and the Square Kilometer Array (SKA).


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