Exploring the Cosmos with Hydrogen Observation

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• Shikhar Mittal (Cavendish)
• Friday 05 December 2025, 11:30-12:30
• Ryle Seminar Room, KICC + online.

If you have a question about this talk, please contact Sandro Tacchella.

The dark ages and cosmic dawn remain among the least explored epochs in our cosmic history. A powerful probe of these periods is the global 21-cm signal. With a growing number of experiments—such as REACH —approaching the sensitivity required to detect this signal, it is essential to develop robust tools for interpreting the forthcoming data. In this talk, I will introduce ECHO21 , a Python package I have developed for modelling the global 21-cm signal from the dark ages through cosmic dawn and up to the end of reionization. Built on an analytic framework, ECHO21 can generate a single signal in O(1) s, enabling the efficient computation of large model grids using multi-core parallelisation. This makes it ideally suited for astrophysical and cosmological inference from upcoming datasets. I will also present my recent work on modelling Lyman-α coupling. Conventional treatments typically neglect the effects of multiple scatterings of Ly-α photons. Our new framework incorporates both multiple scattering and inhomogeneities in the medium, leading to an RMS difference of up to 30% relative to standard calculations. I will conclude by outlining future directions and planned developments.

This talk is part of the Galaxies Discussion Group series.

This talk is included in these lists:

• Cambridge Astronomy Talks
• Combined External Astrophysics Talks DAMTP
• Cosmology, Astrophysics and General Relativity
• Galaxies Discussion Group
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• Kavli Institute for Cosmology Talk Lists
• Ryle Seminar Room, KICC + online
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