Supermassive black holes alter the chemical evolution of galaxies

The results of a new study suggest that highly active supermassive black holes, responsible for generating what are known as quasars in the centers of galaxies, could be responsible for altering the chemical evolution of these galaxies on a large scale.

The study was carried out by a team led by the Center for Astrobiology (CAB), a joint entity of the Higher Council for Scientific Research (CSIC) and the National Institute of Aerospace Technology (INTA), in Spain all of these institutions. The Institute of Astrophysics of Andalusia (IAA) of the CSIC, GRANTECAN of Spain and the Institute of Astronomy and Astrophysics of the Academia Sinica in Taiwan have also participated in the research.

Quasars are one of the most luminous types of objects that we can observe in the universe. Like other active galaxies, they have a supermassive black hole at their center, with masses that vary from millions to billions of times the mass of the Sun, surrounded by a disk of gas that feeds it. The intense gravity of the black hole generates extreme temperatures and pressures in the accretion disk, which causes the emission of intense radiation and the appearance of extreme phenomena such as jets of relativistic particles, which travel at speeds close to that of light, or cosmic winds, flows of gas and particles ejected at thousands of kilometers per second from the inner regions. These winds are capable of injecting large amounts of energy into the rest of the galaxy.

The team responsible for this study made a two-dimensional map of the relative abundances of oxygen and nitrogen in the gas of the active galaxy SDSS 1430+1339, discovered by volunteers from the Galaxy Zoo citizen science project and located more than a billion years away. light of the Earth.

This quasar, colloquially called “Teacup” due to its peculiar shape reminiscent of a teacup, is characterized by the presence of a bubble of hot, ionized gas with a diameter of more than thirty thousand light-years that surrounds its active nucleus. . This bubble is associated with the presence of a huge flow of energy and high-speed particles caused by the activity of its supermassive black hole.

The data obtained demonstrate that this flow, called “superwind”, acts as a powerful energy injection mechanism throughout the galaxy, even affecting the chemical composition of the gas it contains.

Artistic recreation of a superwind generated in the environment of a black hole. (Illustration: ESO / M. Kornmesser. CC BY 4.0)

“Our study shows that the action of this superwind affects the chemical composition of the gas as it passes through the galaxy and that its impact reaches enormous distances,” says Montserrat Villar, CSIC researcher at the Astrobiology Center (CAB) and lead author. of work. “If a similar phenomenon were to occur in the heart of our galaxy, the resulting superwind could contaminate the gas in an enormous volume that would include our solar system with heavy elements,” he clarifies.

The variation in the relative abundances of oxygen and nitrogen observed across the Teacup Galaxy may be compatible with several scenarios. In all of them, the core activity associated with the supermassive black hole acts as the mechanism ultimately responsible for the chemical enrichment of the gas, even at great distances.

“We do not know if the change in chemical abundances in the outer regions has been caused by the displacement of heavy elements from the central region of the galaxy or by other mechanisms that do not involve this drag. Another possibility is that this superwind has induced the formation of stars in areas very far from the galactic core, and that these have enriched the surrounding environment through supernova explosions. In any case, this quasar provides clear observational evidence of how the activity of the nucleus can enrich the gas on large scales, possibly even beyond the galaxy itself,” says Villar.

Sara Cazzoli, researcher at the Institute of Astrophysics of Andalusia and co-author of the study, adds: “Understanding how supermassive black holes regulate the evolution of galaxies is one of the hottest topics in current astrophysics. “The interest of our study lies in the fact that it provides direct evidence of its impact on the chemical evolution of the galaxy.”

The team behind the study used integral field spectroscopy data obtained with the MUSE instrument of the VLT (Very Large Telescope), a set of four 8.2-meter diameter telescopes located at the European Southern Observatory (ESO) facilities in the Chilean Atacama Desert.

The quality of the sky at that location and the sensitivity of the instrument make VLT-MUSE an excellent technological infrastructure, which has made it possible to detect and study in great detail the tenuous ionized gas that surrounds active galaxies as distant as Teacup.

Analysis of the relative abundance and distribution of heavy elements in the gas of galaxies helps reconstruct the history of their chemical evolution, a crucial aspect in star and planetary formation.

“This study is just the beginning, as it can be extended to many other galaxies. We have the theoretical tools and data necessary to investigate whether similar phenomena have occurred at different times in cosmic history,” Villar concludes. (Source: CSIC)