A University of Kansas survey of a belt of the cosmos utilizing the James Webb Space Telescope has disclosed active galactic nuclei—supermassive black holes that are quickly increasing in size—are rarer compared to what several astronomers had supposed earlier.
Image Credit: The University of Kansas
The study outcomes, made with the JWST’s Mid-Infrared Instrument (MIRI), denote the fact that the universe might be a bit more stable than previously thought. Also, the work provides knowledge of observations of faint galaxies, their properties, and difficulties in determining AGN.
A new study elaborating the JWST research, performed under the auspices of the Cosmic Evolution Early Release Science (CEERS) program, was made available on arXiv before formal peer-review publication in the Astrophysical Journal.
The study, headed by Allison Kirkpatrick, Assistant Professor of Physics & Astronomy at KU, concentrated on a long-studied zone of the cosmos dubbed the Extended Groth Strip, situated between the Ursa Major and Boötes constellations. However, earlier examinations of the area depend on a less powerful generation of space telescopes.
Our observations were taken last June and December, and we were aiming to characterize how galaxies looked during the heyday of star formation in the universe.
Allison Kirkpatrick, Assistant Professor of Physics and Astronomy, The University of Kanas
Kirkpatrick added, “This is a look back in time of 7 to 10 billion years in the past. We used the mid-infrared instrument on the James Webb Space Telescope to look at dust in galaxies that are existing 10 billion years in the past, and that dust can hide ongoing star formation, and it can hide growing supermassive black holes. So, I carried out the first survey to search for these lurking, supermassive black holes at the centers of these galaxies.”
While each galaxy features a supermassive black hole in the middle, AGN is a highly spectacular upheaval actively drawing in gases and displaying a luminosity absent from normal black holes.
Kirkpatrick and several fellow astrophysicists forecasted that the higher-resolution JWST survey would locate several more AGNs than an earlier survey, performed with the Spitzer Space Telescope. But even with MIRI’s increase in power and sensitivity, few extra AGNs were discovered in the new survey.
The results looked completely different from what I had anticipated, leading to my first major surprise. One significant revelation was the scarcity of rapidly growing supermassive black holes. This finding was prompting questions about the whereabouts of these objects.
Allison Kirkpatrick, Assistant Professor of Physics and Astronomy, The University of Kanas
Kirkpatrick added, “As it turns out, these black holes are likely growing at a slower pace than previously believed, which is intriguing, considering the galaxies I examined resemble our Milky Way from the past. Earlier observations using Spitzer only allowed us to study the brightest and most massive galaxies with rapidly growing supermassive black holes, making them easy to detect.”
Kirkpatrick stated that a significant puzzle in astronomy lies in comprehending how typical supermassive black holes, like those discovered in galaxies like the Milky Way, grow and impact their host galaxy.
The study’s findings suggest that these black holes are not growing rapidly, absorbing limited material, and perhaps not significantly impacting their host galaxies. This discovery opens up a whole new perspective on black-hole growth since our current understanding is largely based on the most massive black holes in the biggest galaxies, which have significant effects on their hosts, but the smaller black holes in these galaxies likely do not.
Allison Kirkpatrick, Assistant Professor of Physics and Astronomy, The University of Kanas
One more surprising outcome was the absence of dust in such galaxies, stated the KU astronomer.
“By using JWST, we can identify much smaller galaxies than ever before, including those the size of the Milky Way or even smaller, which was previously impossible at these redshifts (cosmic distances),” stated Kirkpatrick.
Kirkpatrick added, “Typically, the most massive galaxies have abundant dust due to their rapid star formation rates. I had assumed that lower mass galaxies would also contain substantial amounts of dust, but they did not, defying my expectations and offering another intriguing discovery.”
According to Kirkpatrick, the work changes the understanding of how galaxies grow, particularly concerning the Milky Way.
Kirkpatrick stated, “Our black hole seems quite uneventful, not displaying much activity. One significant question regarding the Milky Way is whether it was ever active or went through an AGN phase.”
Kirkpatrick added, “If most galaxies, like ours, lack detectable AGN, it could imply that our black hole was never more active in the past. Ultimately, this knowledge will help constrain and measure black hole masses, shedding light on the origins of black holes growing, which remain an unanswered question.”
In recent times, Kirkpatrick earned considerable new time on JWST to perform a bigger survey of the Extended Groth Strip field with MIRI. Her present study included around 400 galaxies. Her upcoming survey (MEGA: MIRI EGS Galaxy and AGN survey) will consist of around 5,000 galaxies. The work is scheduled for January 2024.