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Researchers at the University of Kansas have described a galaxy more than 5.25 billion light years away going through a rarely seen phase in its galactic life cycle. Their findings were recently published on Astrophysical Journal.
The galaxy, dubbed CQ 4479, exhibits features that don’t normally coexist: an active bright X-ray galactic core (AGN) and a supply of cold gas that powers high rates of star formation.
“Huge galaxies, like our own Milky Way, host a supermassive black hole in their heart – these are black holes that grow by accumulating interstellar gas on themselves to become more massive,” said Kevin Cooke, lead author and postdoctoral researcher in KU’s Department. of Physics and Astronomy. “The end of galactic growth is thought to occur when this accretion of gas in the black hole occurs in quantities sufficient to produce a huge amount of energy. So, all the energy surrounding the black hole will actually heat the rest of the gas. the whole galaxy in such a way that it can no longer condense to form stars and the growth of the galaxy stops “.
Instead, the KU researchers found that CQ 4479, a galaxy that had never been closely studied before, is still generating new stars despite the bright AGN at the galaxy’s center.
“Normally, we expect it to shut down everything else,” Cooke said. “But instead, we see huge amounts of new stars forming in this galaxy. So, it’s a very limited window of time in which you can see both the black hole growing and the stars around it growing at the same time.”
The researchers observed the cold quasar primarily using NASA’s SOFIA infrared telescope, which is piloted aboard a Boeing 747. Other measurements were made using FUV-FIR photometry and optical spectroscopy. The work was supported by a NASA grant to principal investigator Allison Kirkpatrick, assistant professor of physics and astronomy at KU, who co-wrote the new paper.
Kirkpatrick said the galaxy observation team’s various methods have shown contradictory data, making the nature of CQ 4479 even more of a puzzle.
“The really unique thing about this source is that we have different measurements of energy production near the black hole,” Kirkpatrick said. “This tells you how fast the black hole is growing and also its feedback in the host galaxy that can stop star formation. We have everything from X-rays, to optics and infrared, so we are able to measure several different signatures. of the black hole’s energy production. And the signatures disagree, it’s really rare. One interpretation is that the black hole’s growth is slowing down, because the X-rays are coming right next to the black hole, while they are coming from a little further away. , and the infrared signatures also come from further away. Basically, it appears that less energy is being produced around the black hole now than in the past. “
Researchers appear to be looking at a snapshot of the galaxy during a key stage in its life.
“I think this is a galaxy in midlife crisis,” Kirkpatrick said. “She’s going through a final explosion of star formation. Most of her solar mass is already in place. She’s forming a few more stars now, and the thing that will eventually kill her is starting to kick in.”
In part, the research at KU was done by Kirkpatrick undergraduate student and co-author Michael Estrada, now a graduate student at the University of Florida.
“He did the optical spectroscopy data analysis and measured the mass of the black hole for us,” Kirkpatrick said.
Other questions remain about the physical structure of the galaxy because the current instrumentation available to astronomers does not provide sufficiently clear images of CQ 4479.
“The image we have shows a central blob and then a small blob below it,” Kirkpatrick said. “So we don’t have a good sense of what this galaxy looks like because the central AGN is so bright that it shines on the rest of the host galaxy. This is a real problem that plagues all AGN studies – when you are dealing with more stuff. bright lights tend to eclipse your host at almost any wavelength. “
The researchers said CQ 4479 would require further study, notably using NASA’s ALMA Observatory and James Webb Space Telescope, the most powerful space telescope ever designed and currently slated to launch on October 31, 2021. Both Cooke and Kirkpatrick they hope to do more investigations into the strange cold quasar once the telescope is launched.
“We are currently focusing on James Webb, because he will have excellent resolution and we should be able to look at the wavelengths where we can see the shape of the galaxy,” said Kirkpatrick. “Another good option would be ALMA. But unfortunately ALMA has temporarily closed due to COVID. We have been a bit hindered from seeing the host galaxy.”
The importance of understanding the strange processes going on in a galaxy 5.25 billion light-years from Earth might seem vague at first, but Cooke said a better understanding of the cold quasar could improve understanding of the cosmos and destiny. of our galaxy.
“This relates a lot to the question ‘where did we come from?’ and “what processes were involved in the creation of the galaxies?” and this is important because we live in a galaxy, “Cooke said. “We live in one of these vast collections of billions of stars and knowing the processes of what created our home is invaluable information. Trying to understand important questions such as these also stimulates important engineering developments here on Earth, such as the technology of detector and all the sophisticated engineering that goes into the SOFIA telescope – there are many ways this kind of work benefits us here on Earth. “
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