Science Goals
My research is targeted towards understanding crucial epochs of the cosmic history. Universe has undergone a series of crucial events from the Big Bang to today. Cosmic dawn, epoch of reionization, and era of dark energy domination are some of the poorly understood periods in this process of evolution.
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I aim to study these epochs by detecting redshifted 21-cm signal from the hydrogen atoms. However, detecting the faint signal is extremely challenging, owing to exceptionally bright foregrounds from our local Universe along with a stringent control on instrumental systematics. Roughly, foregrounds are 100,000 times stronger than the signal!
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We, therefore, build custom radio telescopes that are specifically designed to detect these faint cosmic signatures. Some of these experiments include SARAS and PRATUSH. In addition, I also collaborate with HERA and CHIME experiments. These experiments, while targeting a different measurement technique, are also dedicated towards detecting redshifted hydrogen line from different epochs. ​​
For prospective students
Nature of our research work is fairly diverse. It involves electromagnetic simulations of different telescope designs and calibration strategies of the radiometers. This is followed by development of these designs and their integrated testing in the lab.
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We also test these radiometers at Gauribidanur field station as a first step. Eventually, for precision measurements of the radio sky, we have to deploy at radio quiet sites. We continue to carry out rigorous radio interference survey in different parts of India to find sites that are suitable for science deployments. We have carried out observations from remote regions in Karnataka to wilderness of Ladakh.
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Development of data pipeline, algorithms for modeling instrumental systematics, and devising methods to model foregrounds is another strong focus of our group. These aspects turn into R&D problems since the signal amplitude is extremely faint compared to other components of the observed data. Therefore the analysis schemes need to be tested and validated rigorously to avoid introduction of extra features in the data in the process.
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Finally, the analysis needs to lead to astrophysical constraints at high redshifts. This is in-turn exciting since astrophysics at high redshifts is wide open. We apply Bayesian statistics, along with extensive use of emulators to generate different signal models, to constrain the properties of first stars and galaxies along with the nature of intergalactic medium.
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If you find any (or all!) of this interesting, we are accepting PhD students, postdocs, and visiting students. Feel free to write me an email for more details.
Resources
A brief description of 21-cm cosmology can be found here. For a more detailed approach, this is an excellent review paper on the subject. ArXiv is a great place to be updated with the latest research in the field. Essential Radio Astronomy is a great introduction to working principles in radio telescope design and development.
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My latest research, including several significant astrophysical constraints placed by our experiments, can be found on my Google Scholar page. One of my talks describes the status of the field and highlights some of our recent work.
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For aspiring researchers, I would strongly recommend to read Four Golden Lessons by Steven Weinberg. In the same spirit, The importance of stupidity in scientific research by Martin Schwartz is another insightful article.