Astronomers in Pune have discovered why the rate of star formation in galaxies in our universe slowed down about eight billion years ago.
TIFR – A group of scientists from the National Center for Radio Astrophysics (NCRA) made this conclusion based on observations of a decreasing amount of atomic hydrogen gas from 9 billion to 8 billion years ago today. These observations, lasting 510 hours, were obtained between 2018 and 2020 using the Advanced Giant Meterwave Radio Telescope (UGMRT).
Gaseous matter is abundant in galaxies and our universe, which is thought to be about 13.8 billion years old, had higher and more frequent rates of star formation during its youth. The highest star births were recorded between 8 and 10 billion years ago. This is because galaxies contain high concentrations of gaseous matter – one of the main drivers for star formation. Furthermore, the rate of star formation was almost constant between 11 billion – 9 billion years ago.
However, after 8 billion years, a different trend emerged, but the reasons were not completely scientifically correct.
Established.
Scientists at NCRA studied the atomic gas in galaxies by observing a spectral line of wavelength about 21 cm in the hydrogen atom. Because these spectral lines are faint and weak, the researchers stacked the 21cm signals from known galaxies in a technique called spectral line stacking.
“A declining trend was observed in the rate of star formation in galaxies 8 billion years ago,” said Aditya Choudhary, a final year PhD student at NCRA and lead author of the new study published in The Astrophysical Journal Letters.
While galaxies stop giving birth to stars by exhausting all their gas, it is also possible that they may obtain nuclear gas from their surroundings.
Study co-author, NCRA’s Jayaram Chengalur, said, “The only way to test whether gas reserves have been consumed or replenished is the atomic gas masses of these galaxies at two different periods in the universe.” have to measure.”
Nissim Kanekar, a scientist at NCRA and another co-author of the paper, said that galaxies eight billion years ago had about three times less nuclear gas than galaxies with similar stellar masses nine billion years ago.