Black hole jet may be stirring gas cloud containing early ‘red potato’ galaxy

A black hole may be stirring a “pot” of gas containing a neighboring galaxy in the early universe, according to a new study published in Astronomy & Astrophysics that used observations from NASA’s Chandra X-ray Observatory. The galaxy slowly being “cooked” is named MQN01 J004131.9-493704, but astronomers have nicknamed it the “red potato” because of its appearance in images from NASA’s James Webb Space Telescope.

The red potato galaxy is located about 11.7 billion light-years from Earth at an intersection where gigantic web-like structures of galaxies and gas meet. Astronomers targeted this area with Webb because they knew it contained one of the heaviest concentrations of galaxies and growing supermassive black holes yet identified in the early universe.

A missing burst of stars

Data from the European Southern Observatory’s Very Large Telescope show that the red potato galaxy is surrounded by an enormous cloud, or “pot,” of relatively cold gas. Astronomers expected it to have large numbers of young stars that formed after some of the gas was pulled into the galaxy. This has been seen for nearby galaxies surrounded by cold gas, but, surprisingly, not for the red potato.

“Stars are not forming like we thought they would, so we went searching for the reason why,” said Weichen Wang of the University of Milan-Bicocca in Italy, who led the new study. “We found there may be a cook in this cosmic kitchen.”

One important clue is that the cloud of gas surrounding the red potato galaxy is unusually turbulent compared with large gas clouds surrounding other galaxies. Such turbulence could be preventing most of the gas from falling onto the red potato galaxy to form large numbers of new stars.

A neighbor’s jet as culprit

Wang and his colleagues then searched for the origin of this turmoil. Using Chandra, they discovered that a jet of particles from a black hole in a neighboring galaxy is pointed toward and may be striking the gas cloud around the red potato galaxy, possibly causing the turbulence.

“If the black hole’s jet is stirring up the gas around the red potato, it could greatly slow down how quickly the galaxy can acquire new, fresh material to form stars,” said co-author Sebastiano Cantalupo, also of the University of Milan-Bicocca. “With the energy from the stirring, the galaxy will starve and not be able to produce new stars at the rate expected for similar galaxies at the same cosmic epoch.”

While the red potato galaxy mostly has older, cooler stars and therefore appears red in optical and infrared data, the galaxy hosting the black hole with the jet does not. Instead, this galaxy, which is located about 200,000 light-years from the red potato, is very actively forming stars, including massive, hot stars, as are most of the other nearby galaxies.

Astronomers want to learn how galaxies and black holes interact with each other—especially at this critical epoch in the universe’s history—and how that affects when and how stars form.

“The red potato is leaving crumbs of information that may help us track down the answers to some really big questions,” said co-author Andrea Travascio, also of the University of Milan-Bicocca. “Quite an important job for a galactic spud like this.”

Other causes look less likely

The authors considered other explanations for making the gas turbulent, including outbursts from a supermassive black hole in the center of the red potato galaxy itself or energy from a burst of new stars forming. However, they consider these explanations less likely than the neighboring galaxy’s jet.

This work is one of the few published studies to probe the behavior of gas surrounding passive galaxies in the early universe like the red potato, found at distances greater than about 11 billion light-years from Earth.

Data from NASA’s Hubble Space Telescope was also used to support the measurements needed to reveal the galaxy’s red color and low rate of star formation.

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Lisa Lock

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