The early universe should be full of active galaxies, but JWST doesn’t find them

For decades, quasars were the most distant objects we could see. We now know that they are powerful active black holes.

Active galactic cores are so distant that they resemble star-like points of light.

It shows us that supermassive black holes in the early Universe can be powerful monsters driving the evolution of their galaxies.

We had assumed that most early supermassive black holes went through such an active phase, but a new study suggests that this is not the case for most supermassive black holes.

Most galaxies contain a supermassive black hole. They contain millions or billions of solar masses.

They can propel massive jets of ionized gas blasting away from a galaxy at nearly the speed of light, rip stars apart to seed a galaxy with gas and dust, and even purge dust from galaxies to prevent star formation.

They can also remain dormant for billions of years, hiding in a galaxy’s central bulge, as is the case with the central black hole in the Milky Way.

But the sheer mass of these black holes suggests that they must have grown rapidly in their youth, suggesting a period of extreme activity similar to that of distant quasars.

That is new study deals with a period of cosmic history known as Cosmic Noon. It is the time when the universe was around 3 to 6 billion years old and marks the age when stellar production in the universe peaked.

This is also about the time we would expect supermassive black holes to be active, since their churning of gas and dust can trigger star formation.

Using the James Webb Space Telescope, the team collected data from a stretch of sky known as the Extended Groth Strip (ESG).

The ESG is a small, barren region of sky between the constellations Ursa Major and Boottes. It was observed in detail by the Hubble Space Telescope in 2004 and 2005, finding more than 50,000 galaxies.

In 2011, the Spitzer Space Telescope observed the region in infrared wavelengths as part of the All-Wavelength Extended Groth Strip International Survey (AEGIS). Spitzer saw the glow of many active black holes, but not as many as expected.

This was not too unexpected as it was quite possible that Spitzer was not sensitive enough to detect smaller or deeply dust-shrouded AGNs.

This new survey from JWST expected more, but it wasn’t the case. The Cosmic Evolution Early Release Science program (CEERS) has found about the same number of active black holes as before.

And with the higher resolution and sensitivity of JWST, we can just ignore the conclusions.

What this team found is that active black holes are rare during cosmic noon, meaning most galactic black holes grow more slowly.

The team also found that there was not a large amount of dust in smaller galaxies.

Many of the observed galaxies resembled the Milky Way. Spiral galaxies with little dust and a fairly central black hole. This raises the possibility that our galaxy never had an AGN period.

Note that this first result only focuses on about 400 galaxies. The team plans to conduct a larger survey of 5,000 galaxies over the next year.

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Written by Brian Koberlein/universe today.