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James Webb Telescope Reveals 14 ‘Sleeping’ Galaxies in Early Universe
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August 29, 2024
Washington D.C. – In a groundbreaking discovery, astronomers using teh James Webb Space Telescope (JWST) have identified 14 galaxies that appear to have ceased star formation much earlier than previously thought, offering new insights into the evolution of the universe. The findings, published in the journal Nature on August 28, 2024, challenge existing models of galaxy evolution and suggest a more complex picture of the early cosmos.
These galaxies, observed as they existed approximately 600 to 700 million years after the Big Bang (redshift z ≈ 7-9), are described as “quiescent” – meaning they have largely stopped forming new stars. Prior to JWST, astronomers believed that significant star formation continued in most galaxies during this epoch. The discovery indicates that at least some galaxies matured and halted star formation surprisingly quickly.
The research team, lead by Dr. Jeyhan Kartaltepe of the Rochester Institute of Technology, analyzed data from the JWST’s Near Infrared Camera (NIRCam) and Near Infrared Spectrograph (NIRSpec) instruments. The observations revealed a lack of ongoing star formation indicators, such as strong emission lines from ionized hydrogen, in these 14 galaxies. The galaxies are relatively small, with masses comparable to the Small Magellanic Cloud, a dwarf galaxy orbiting the Milky Way.
“These galaxies are like sleeping babies,” explains Dr.Kartaltepe.”They formed stars early in the universe, then seemingly whent quiet, halting their star formation much sooner than we expected. Understanding why this happened is a key question for cosmology.”
Understanding Galaxy Quenching
The process by which galaxies cease star formation is known as “quenching.” Several mechanisms can contribute to quenching, including:
- Gas Accretion Shutdown: Galaxies require a constant supply of gas to fuel star formation. If the inflow of gas is cut off,star formation will eventually decline.
- supermassive Black Hole Feedback: Active galactic nuclei (AGN), powered by supermassive black holes at the centers of galaxies, can release enormous amounts of energy that heat and expel gas, suppressing star formation.
- Mergers and Interactions: Galactic mergers can disrupt gas clouds and trigger bursts of star formation, but can also eventually lead to quenching as the gas is consumed or expelled.
The researchers hypothesize that the observed quenching in these early galaxies may be due to a combination of factors, potentially including early black hole growth and feedback, or the effects of early galactic interactions.Further investigation is needed to determine the dominant mechanisms at play.
Implications for Cosmology
This discovery has significant implications for our understanding of the early universe and the formation of galaxies. It suggests that the early universe was more diverse than previously thought, with a wider range of galaxy
