Janakee Raste

Post-Doctoral Fellow
Email: janakee [at] ncra.tifr.res.in
Phone: 020-25719295
Extn: 9295
Office: 218D
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA

Main Research Areas: Cosmology; HI 21 cm line studies; The Epoch of Reionization; Cosmic Dawn


Janakee completed her B.Tech in Information and Communication Technology (ICT) from Dhirubhai Ambani Institute of Information and Communication Technology (DAIICT) in 2012. She then joined the the Joint Astronomy Programme (JAP) at the Indian Institute of Science (IISc) for her doctoral studies, obtaining her Ph.D. in 2019. She was next a post-doctoral fellow at the Tata Institute of Fundamental Research, Mumbai, from September 2019 to August 2022. She joined NCRA as a post-doctoral fellow in September 2022.

Research description:

The epoch when the first stars and galaxies were formed in the Universe is referred to as Cosmic Dawn. The earliest sources of radiation ionized the neutral hydrogen gas in the surrounding intergalactic medium during the Epoch of Reionization. These epochs hold the key to understanding the formation of large-scale structure, the properties of the first luminous sources, and the nature of dark matter. My work is primarily focused on understanding these epochs, using the 21 cm and the Lyman-alpha lines of hydrogen. I have developed an analytical formalism to compute the two-point correlation function and the power spectrum of the 21 cm signal during Cosmic Dawn, over the redshift range 20<z<10. I have also studied the 21 cm power spectrum from the late end of reionization and predicted the sensitivity of the present and upcoming interferometric instruments to detect this signal. To study the non-gaussianity of large neutral hydrogen islands left at the end of reionization, I have also analysed the bispectrum of the 21 cm signal.

Selected publications:

1. The 21-cm bispectrum from neutral hydrogen islands at z < 6  (J. Raste et al. 2024, MNRAS, 529, 129)

2. Implications of the z>5 Lyman-α forest for the 21-cm power spectrum from the epoch of
reionization (J. Raste et al. 2021, MNRAS, 507, 4684)

3. Analytic formulation of 21 cm signal from cosmic dawn: Lyα fluctuations (J. Raste and S. Sethi 2019, ApJ, 876, 56)

4. An Analytic Formulation of the 21 cm Signal from the Early Phase of the Epoch of Reionization (J. Raste and S. Sethi 2018, ApJ, 860, 55)