Astronomers from the Astrophysics in Pune and the Raman Research Institute, Bengaluru, using the upgrade Giant Metrewave Radio Telescope (GMRT), measured the atomic hydrogen content of galaxies as they were eight billion years ago to understand the decrease in star formation.
The research paper conducted by astronomers was published in the Nature Journal. It established that the galaxies rapidly uses atomic hydrogen for their high star formation activity. This activity is the primary fuel for star formation. The last for the next one to two billion years estimate hydrogen. This leads to a decrease in star formation later. Studying hydrogen gas and stars is an essential element in understanding the galaxy.
Studies showed that the star formation rate was much higher around eight billion years ago than what it is now.
Aditya Chowdhury, a doctoral student at NCRA-TIFR and the lead author of the study, said, “This 21cm signal is feeble and difficult to detect from distant individual galaxies even with powerful telescopes like the upgraded GMRT. We overcome this limitation by using a technique called ‘stacking.’ It combines the 21 cm signals of nearly 8000 galaxies identified with optical telescopes. This method measures the average gas content of these galaxies.”
Last one-two billion years
The atomic hydrogen signal lies in the radio wavelength of 21 cm. This is unlike the stars that emit intense light at an optical wavelength. A wavelength that detects only by radio signals.
The star formation, scientists found, was intense in the initial stages of the universe’s construction. The atomic gas in and around the galaxies are consumed by star formation. This will be in just one or two billion years. Choudhary said:
“If galaxies can not acquire more hydrogen from their surroundings, the star formation activity would decline AND finally, cease in these galaxies.”
The study using the 21 cm signal has measured the atomic hydrogen mass in the universe’s galaxies. It has successfully shown that hydrogen is enough to sustain star formation for only one to two billion years.
Tribute to the founder of GMRT
The team of scientists at the National Centre for Radio Astrophysics in Pune and the Raman Research Insitute, Bengaluru, used 90 hours of GMRT time for observation and study. They took almost six months to analyze the data.
According to the scientists of this research, the discovery is a tribute for Govind Swarup. He is the father of radio astronomy in India who set up GMRT. He passed away in September.
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