July 25, 2022 Reviewed by Alex Smith
Using data from the Atacama Large Millimeter Array (ALMA) and the Very Large Telescope (VLT) of the European Southern Observatory (ESO), a European team of astronomers measures the gas pressure and studies how the powerful jets of a supermassive black hole alters the conditions. for star formation in interstellar clouds.
The pressure maps of IC 5063. The left panel shows the internal pressure of the molecular clouds measured from CO and HCO+ emission lines. The right panel shows the pressure of the ionized medium measured from the emission lines of ionized sulfur and nitrogen. This pressure is considered external to the molecular clouds. The crosses mark the position of the radio core and the white contour lines of the jet trace as traced by the narrow-band image from the Hubble Space Telescope’s Wide Field Planetary Camera 2. Image credit: University of cologne
A European group of astronomers led by Professor Kalliopi Dasyra of the National and Kapodistrian University of Athens, Greece, with the participation of Dr. Thomas Bisbas of the University of Cologne, modeled numerous emission lines at the Atacama Large Millimeter Array (ALMA) and Very Large Telescope (VLT) observations to quantify gas pressure in both ambient and jet-impacted clouds .
With these unprecedented predictions, recently reported in the journal Nature Astronomy, the researchers discovered that the jets greatly alter the internal and external pressure of the molecular clouds in their path.
In the same galaxy, it is possible for clouds to compress and initiate star formation, as well as for clouds to dissipate and delay star formation, depending on which of the two pressures changes more.
Our results show that supermassive black holes, although located at the center of galaxies, could affect star formation in a galaxy-wide way. Studying the impact of pressure changes on cloud stability was key to the success of this project. Once a few stars form in a wind, it is usually very difficult to detect their signal above the signal of all the other stars in the galaxy hosting the wind.
Kalliopi Dasyra, Professor, Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, National and Kapodistrian University of Athens
Supermassive black holes are believed to be at the center of most galaxies in the Universe.
When particles that were intrusive into these black holes have been trapped by the magnetic fields, they could be ejected outwards and travel further into the galaxies in the form of large, powerful jets of plasma.
These jets are often perpendicular to the galactic discs. But in a galaxy 156 million light-years away called IC 5063, the jets are actually generated inside the disk, interacting with clouds of dense, cold molecular gas.
Based on this interaction, it has been theorized that compression of jet-impacted clouds is possible. This causes gravitational instabilities and eventually star formation as a result of gas condensation.
For the experiment, the research group used formyl cation (HCO+) and carbon monoxide (CO) emission provided by ALMA and ionized nitrogen and ionized sulfur emission provided by VLT. They then made use of sophisticated and innovative astrochemical algorithms to detect the environmental conditions of the outflow and the surrounding medium.
These environmental conditions include data on the strength of far-ultraviolet radiation from stars. This is the rate at which relativistic charged particles ionize the gas, and then mechanical energy is deposited on the gas by the jets.
Narrowing down these conditions revealed illustrative gas densities and temperatures for various parts of this galaxy, which were further used to provide pressures.
“We performed 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 researcher at the National Observatory of Athens. .
A challenging aspect of the work was to carefully determine as many physical constraints as possible on the analyzed range that each parameter could have.
In this way, we could obtain the optimal combination of physical parameters of the clouds in different places of the galaxy.
Georgios Filippos Paraschos, co-author of the study and PhD student, Max Planck Institute for Radio Astronomy
Georgios Filippos Paraschos was a master’s student at the National and Kapodistrian University of Athens.
In fact, the pressures were not only quantified for a few locations in IC 5063. Rather, they mapped this and other quantities at the center of this galaxy. These maps allowed the authors to imagine how the properties of the gas change from one location to another due to the passage of the jet.
Currently, the team is looking forward to using the James Webb Space Telescope for further investigations of the pressure in the outer cloud layers, as evidenced by warm H2.
We are really excited about getting the JWST data, as it will allow us to study the jet-cloud interaction at exquisite resolution.
Kalliopi Dasyra, Professor, Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, National and Kapodistrian University of Athens
Journal reference:
Dasyra, KM, et al. (2022) Insights into the collapse and expansion of molecular clouds in observable pressure gradient outflows. Astronomy of nature. doi.org/10.1038/s41550-022-01725-9
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