Supermassive black holes prevent star formation

(ORDO NEWS) — The Milky Way galaxy is made up of stars of all ages, including stars that are still forming. But in the galaxies known as ellipticals, all the stars are old and about the same age.

This indicates that at the beginning of their history, elliptical galaxies had a period of active star formation, which ended abruptly.

Why this star formation stopped in some galaxies and not in others is not entirely clear. One possibility is that a supermassive black hole is destroying the gas in some galaxies, creating an environment unsuitable for star formation.

To test this theory, astronomers observe distant galaxies. Due to the finite speed of light, it takes time for it to overcome the void of space.

The light we see from the object had to travel 10 billion years to reach Earth. Thus, looking at distant galaxies, we seem to look into the past. The most distant galaxies appear much dimmer, making them difficult to study.

To overcome these difficulties, an international team led by Kei Ito of SOKENDAI in Japan used the Cosmic Evolution Survey (COSMOS) program to sample galaxies at a distance of 9.5-12.5 billion light-years. COSMOS includes data on radio waves, infrared light, visible light, and X-rays.

First, the team used optical and infrared data to identify two groups of galaxies: those in which star formation continues and those where star formation has ceased.

The signal-to-noise ratio of the X-ray and radio wave data was too weak to identify individual galaxies. So the team combined various data to get images of “average” galaxies with a higher signal-to-noise ratio.

Using averaged images, the team confirmed the presence of X-ray and radio emission from galaxies without star formation.

For the first time, such radiation was detected for distant galaxies at a distance of more than 10 billion light years. In addition, the results show that the X-ray and radio emission is too strong to be explained by the presence of stars in the galaxy alone, indicating the presence of an active supermassive black hole.

The signal about black hole activity is weaker for galaxies in which star formation continues.

These results show that the abrupt cessation of star formation in the early universe is correlated with increased SMBH activity.


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