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Supermassive black holes affect star formation

A European team of astronomers led by Professor Kalliopi Dasyra at the National and Kapodistrian University of Athens, Greece, with the participation of Dr. Thomas Bisbas, University of Cologne modeled several emission lines in the Atacama Large Millimeter Array (ALMA) and Very Large Telescope (VLT) observations to measure the gas pressure in both jet-affected clouds and surrounding clouds. With these unprecedented measurements, recently published in Nature astronomy, they discovered that the jets significantly change the internal and external pressures of molecular clouds in their path. Depending on which of the two pressures changes the most, both cloud compression and star formation triggering and cloud disappearance and star formation delay are possible in the same galaxy. “Our results show that supermassive black holes, even if they are located at the center of galaxies, can affect star formation in a galaxy-wide way,” said Professor Dasyra, adding that “studying the effect of pressure changes on the stability of clouds was key to the success of this project . When few stars actually form in a wind, it is usually very difficult to detect their signal on top of that of all the other stars in the galaxy hosting the wind.”

Supermassive black holes are believed to lie at the center of most galaxies in our universe. When particles that were falling into these black holes are captured by magnetic fields, they can be ejected and travel far into galaxies in the form of huge and powerful jets of plasma. These rays are often perpendicular to galactic discs. In IC 5063, a galaxy 156 million light-years away, the jets actually propagate within the disc and interact with cold and dense molecular gas clouds. From this interaction, compression of jet-influenced clouds is theorized to be possible, leading to gravitational instability and eventually star formation due to gas condensation.

For the experiment, the team used the carbon monoxide (CO) and formyl cation (HCO+) emissions from ALMA, and the ionized sulfur and ionized nitrogen emissions from the VLT. They then used advanced and innovative astrochemical algorithms to pinpoint the environmental conditions in the outflow and in the surrounding medium. These environmental conditions contain information about the strength of the far-ultraviolet radiation from stars, the rate at which relativistically charged particles ionize the gas, and the mechanical energy deposited on the gas by the rays. Reducing these ratios revealed the densities and gas temperatures describing different parts of this galaxy, which were then used to provide pressure.

“We have performed many thousands of astrochemical simulations to cover a wide range of possibilities that may exist in IC 5063,” said co-author Dr. Thomas Bisbas, DFG Fellow at the University of Cologne and former postdoctoral fellow at the National Observatory of Athens. A challenging part of the work was to accurately identify as many physical constraints as possible to the surveyed area that each parameter could have. “In this way, we were able to obtain the optimal combination of physical parameters for clouds in different locations in the galaxy,” said co-author Georgios Filippos Paraschos, Ph.D. student at the Max Planck Institute for Radio Astronomy in Bonn and former master’s student at the National and Kapodistrian University of Athens.

In fact, the pressures were not just measured for a few locations in IC 5063. Instead, maps were created of this and other quantities in the center of this galaxy. These maps allowed the authors to visualize how gas properties change from one location to another due to the passage of the jet. The team is currently looking forward to the next major step in this project: using the James Webb Space Telescope for further investigations of the pressure in the outer cloud layers, as probed by the warm H2. “We are really excited to get the JWST data,” said Professor Dasyra, “because it will enable us to study the jet-cloud interaction at an exquisite resolution.”

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Material provided by University of Cologne. Note! Content can be edited for style and length.

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