Colloquium on Apr. 15, 2021

Seeing the first dawn through the eyes of hydrogen

Speaker: Suman Majumdar (IITI)

Venue: Video Conference

Time: 16:00 PM, Thursday, Apr. 15, 2021

Abstract:

The first starlight was produced in the Cosmic Dawn (CD), when the first stars, first galaxies, and first black holes formed around 100 million years after the Big Bang. Although we know such a moment must occur, astronomers have yet to directly observe this era in cosmic history. These sources of light are expected to have generated a huge amount of radiation in X-ray and UV, which have gradually heated up and ‘re’-ionized most of the visible matter in the Universe -- hydrogen. So far, our knowledge of this phase is mostly based on some indirect observations that do not answer many fundamental questions regarding this era: When did it start? How long did it take? How did it develop in time? What are major sources that produced heating and ionizing photons and how were they distributed in space?

Radio interferometric observations of the redshifted 21-cm signal, originating from spin-flip transitions in hydrogen atoms from this era, is the most promising and direct probe of the CD and could potentially resolve many of these puzzles. The upcoming next-generation radio telescope, the Square Kilometre Array - SKA, will be able to observe it in great detail. One would require optimal analytical tools to interpret the upcoming complex, high volume, and high-resolution radio observations from this era. In this talk, I will discuss one such statistical tool, the CD 21-cm bispectrum, which can be used potentially to understand the IGM physics, constrain the CD parameters and understand the nature of the dark matter.

Report PPT:  SWIFAR_Suman Majumdar.pdf