Wednesday
05
November 2025
2:30 - 4:00 PM IST
Location
Room 301, School of Arts and Sciences
Central Campus
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From First Stars to Reionization: A Statistical Study of Neutral Hydrogen
Arts and Sciences Research Seminar Series
Janakee Raste
Post Doctoral Fellow
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research, Pune
Speaker
In the first billion years after the Big Bang, the first stars and galaxies formed in the Universe in an epoch called Cosmic Dawn. They emitted a broad spectrum of radiation, heating and ionising the intergalactic medium during the Epoch of Reionisation. To study these epochs, one of the most promising probes is the faint 21-cm radio signal from neutral hydrogen, which carries key information about the thermal and ionisation history of the early Universe. In this talk, I will introduce the physics behind this signal and explain how it is shaped by radiation from the first luminous sources. I will then present my work on analytical modelling, numerical simulations, and statistical tools that can help us predict and interpret the 21-cm signal from ongoing and upcoming radio experiments.
Speaker
Janakee Raste
Her research work is primarily focused on understanding the epochs of Cosmic Dawn (CD) and Reionization (EoR), using the 21-cm and the Lyman-alpha lines of hydrogen. She has worked on analytical formalisms and semi-numerical codes to predict the two-point correlation function, power spectrum, and bispectrum of the 21-cm signal from CD/EoR, as well as the sensitivity of the present and upcoming interferometric instruments to detect this signal. Her recent work focuses on a deeper analysis of energy exchange between Lyman-alpha photons and the neutral hydrogen at high redshifts and its implications for the 21-cm signal.
