Aditya Chowdhury
Research Scholar
Email: chowdhury [at] ncra.tifr.res.in
Phone: +91 - 20 - 25719458
Extn: 9458
Office: F250
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA
Main Research Areas: 21cm Cosmology; Atomic Hydrogen in High Redshift Galaxies; Cosmic Dawn;
Biography:
Aditya obtained his B.Sc. from St. Xavier's College, Kolkata, in 2015. While at St. Xavier's College, he did his final year project on constraining the Hubble constant and the dark matter density using supernovae data from multiple sources. He joined NCRA-TIFR as an Integrated Ph.D. scholar in the same year. He completed the NCRA-TIFR Graduate School requirements in 2018, and is now working with Nissim Kanekar and Jayaram Chengalur for his doctoral research.Research description:
Atomic Hydrogen in High Redshift Galaxies
Neutral atomic hydrogen is a key constituent in galaxies and plays an important role in galaxy evolution as the primary fuel for star formation. It has been known for close to two decades that 8 to 10 billion years ago, galaxies formed ten times more stars per year than they do today in the local Universe. In fact, half the stars that we see today were formed in this period, which is hence called the epoch of galaxy assembly. However, we know little about the atomic hydrogen gas in these galaxies which fuelled the high star formation activity. We are currently using the upgraded Giant Metrewave Radio Telescope (GMRT) to carry out very sensitive surveys for HI 21cm emission from star-forming galaxies at high redshifts to address this issue. Initial GMRT data from our pilot survey has yielded the first measurement of the atomic hydrogen content in galaxies at the peak of cosmic star formation. We are now completing an even larger GMRT HI 21cm survey that will lead to a detailed characterization of atomic hydrogen in galaxies at the end of the epoch of galaxy assembly. We are also beginning a new survey to push these measurements to even higher redshifts, at the peak of the star-formation activity of the Universe. These observations will provide an understanding of the build-up of atomic hydrogen in galaxies and its connection to the star formation history over the past 11 billion years.
Neutral atomic hydrogen is a key constituent in galaxies and plays an important role in galaxy evolution as the primary fuel for star formation. It has been known for close to two decades that 8 to 10 billion years ago, galaxies formed ten times more stars per year than they do today in the local Universe. In fact, half the stars that we see today were formed in this period, which is hence called the epoch of galaxy assembly. However, we know little about the atomic hydrogen gas in these galaxies which fuelled the high star formation activity. We are currently using the upgraded Giant Metrewave Radio Telescope (GMRT) to carry out very sensitive surveys for HI 21cm emission from star-forming galaxies at high redshifts to address this issue. Initial GMRT data from our pilot survey has yielded the first measurement of the atomic hydrogen content in galaxies at the peak of cosmic star formation. We are now completing an even larger GMRT HI 21cm survey that will lead to a detailed characterization of atomic hydrogen in galaxies at the end of the epoch of galaxy assembly. We are also beginning a new survey to push these measurements to even higher redshifts, at the peak of the star-formation activity of the Universe. These observations will provide an understanding of the build-up of atomic hydrogen in galaxies and its connection to the star formation history over the past 11 billion years.
Selected publications:
1. Insufficient Gas Accretion Caused the Decline in Cosmic Star-formation Activity Eight Billion Years Ago (A. Chowdhury, N. Kanekar, J.N. Chengalur 2022, ApJL, 931, L34) 2. Giant Metrewave Radio Telescope Detection of HI 21 cm Emission from Star-forming Galaxies at z ~1.3 (A. Chowdhury, N. Kanekar, B. Das et al. 2021, ApJL, 913, L24) 3. HI 21-centimetre emission from an ensemble of galaxies at an average redshift of one (A. Chowdhury, N. Kanekar, J. N. Chengalur, et. al. 2020, Nature, 586, 369) 4. Giant Metrewave Radio Telescope Detections of Two High-opacity HI 21 cm Absorbers at z ~ 1.2 (A. Chowdhury, N. Kanekar & J. N. Chengalur 2020, ApJL, 900, 2, L30) 5. A High Resolution Study of Carbon Radio Recombination Lines towards Cassiopeia A (A. Chowdhury & J. N. Chengalur 2019, MNRAS, 486, 42) 6. A dearth of atomic hydrogen in NGC 1052-DF2 (A. Chowdhury 2019, MNRAS Letters, 482, 99) 7. Angular momentum content in gas-rich dwarf galaxies (A. Chowdhury & J. N. Chengalur 2017, MNRAS, 467, 3856) 8. The Dielectric Breakdown Model applied to explain various morphologies of deposited metallic structures in thin gap metal electro-deposition. (A. Chowdhury & D. Dutta 2015, AIP Advances, 5, 067120)
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