For decades, the most distant objects we could see were quasars. Now we know that these are powerful active black holes. Active galactic nuclei (AGNs) are so far away that they resemble star-like points of light. According to this, supermassive black holes in the early universe could be huge monsters that control the evolution of galaxies.
Until now, we thought that most of the early supermassive black holes went through such an active phase, but a new study shows that most of them do not, reports Universe Today.
Most galaxies contain a supermassive black hole with millions or billions of solar masses. They can blast their massive jets of ionized gas out of a galaxy at nearly the speed of light, rip apart stars to fill galaxies with gas and dust, and even strip galaxies of dust from the moment stars are born. Galaxies can remain at rest for billions of years and collapse at the center of the galaxy, as happens with the black hole of the Milky Way. However, the sheer mass of these objects suggests that they may have grown rapidly in their youth, suggesting a period of extreme activity similar to distant quasars.
We don’t know why we can’t find them.
This article focuses on the period of cosmic history known as the Cosmic South. This is the period when the universe was about 3–6 billion years old and when star formation in the universe was at its peak. This is the period when supermassive black holes are expected to be active as they can trigger star formation by churning gas and dust. Using the James Webb Space Telescope, the research team collected data from a region of the sky known as the Extended Growth Streak (ESG).
ESG is a small barren area between the constellations Ursa Major and Ursa Major. The Hubble Space Telescope observed it in detail in 2004 and 2005 and found over 50,000 galaxies. In 2011, the Spitzer Space Telescope observed the region in infrared as part of the International All Wavelength Growth Band Survey (AEGIS). Spitzer saw the glow of many active black holes, but not as many as expected. This was not too surprising since Spitzer may not have been sensitive enough to see smaller, dusty AGNs or active galactic nuclei.
Theoretically, the new JWST poll should have seen more, but that didn’t happen. The Cosmic Evolution Early Release Science (CEERS) program has found about the same number of active black holes as before. And thanks to the higher resolution and sensitivity of JWST, we can simply dismiss such conclusions.
The research team found that active black holes are rare during cosmic noon, meaning that most galactic black holes grow more slowly. The team also found that smaller galaxies don’t have huge amounts of dust inside. And many of the observed galaxies resembled the Milky Way. They were spiral galaxies with little dust and a central black hole. This suggests the possibility that our galaxy never had an AGN period.
It should be noted that this initial result concerns only about 400 galaxies. The research team plans to conduct a larger study of 5,000 galaxies next year.