Supermassive black holes alter the chemical evolution of galaxies

Quasars are among the most luminous objects known in the universe. Like other active galaxies, they host a supermassive black hole at their center, with masses that vary from millions to billions of times the mass of the Sun. It is surrounded by a disk of plasma that feeds it. The enormous gravitational pull of the black hole generates extreme temperature and pressure in this accretion disk. This causes the emission of an intense radiation and triggers 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 internal regions. These processes are capable of injecting large amounts of energy into the rest of the galaxy.

A research led by the Center for Astrobiology (CAB, INTA-CSIC, Spain) with the participation of the Institute of Astrophysics of Andalusia (IAA-CSIC, Spain), the Institute of Astronomy and Astrophysics of the Academia Sinica (Taiwan) and GRANTECAN (Spain), suggests that these extreme phenomena generated by the activity of supermassive black holes could be responsible for altering the chemical evolution of the entire galaxy.

A “cup of tea” shaped by superwinds

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

This quasar, nicknamed the “Teacup” due to its peculiar shape reminiscent of a teacup, is characterized by the presence of a giant bubble of hot and 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 Teacup galaxy seen by the Hubble Space Telescope. Credit: NASA, ESA, W. Keel (University of Alabama), and the Galaxy Zoo Team

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

“Our study shows that the superwind has changed the chemical composition of the gas as it passes through the galaxy. We see that its impact reaches enormous distances,” says Montserrat Villar Martín, astrophysicist at the Center for Astrobiology (CSIC-INTA) and main author of the work. “If a similar phenomenon occurred at the heart of our galaxy, the superwind could contaminate the gas with heavy elements across an enormous volume that would include the Solar System”.

The black hole as driver of chemical evolution

The variation in the relative abundances of oxygen and nitrogen observed across the Teacup Galaxy is compatible with several scenarios. In all of them, the nuclear activity associated with the supermassive black hole acts as the ultimate mechanism 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 dragging of heavy elements from the central region of the galaxy or by other mechanisms that do not involve this displacement. Another possibility is that the superwind has induced the formation of stars in regions 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 nuclear activity can enrich gas on large scales, possibly even beyond the galaxy itself,” says Montserrat Villar Martín.

Sara Cazzoli, researcher at the Instituto de Astrofísica de Andalucía (CSIC, Spain) 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 that it provides direct evidence of its impact on the chemical evolution of the galaxy.”

Artist's impression of a superwind generated in the environment of a black hole. Credit: ESO/M. Kornmesser

From the Atacama desert

The team responsible for this study used integral field spectroscopy data obtained with the MUSE instrument of the Very Large Telescope (VLT), 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 allowed to detect and study in great detail the tenuous ionized gas that surrounds active galaxies as distant as the Teacup.

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

“This study is just the beginning, as it can be applied 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,” concludes Montserrat Villar Martín.

Very Large Telescope (VLT). Credit: ESO

About IAA-CSIC

The Instituto de Astrofísica de Andalucía (IAA) is a research institute  of the Spanish Research Council (Consejo Superior de Investigaciones Científicas, CSIC). Its mission is to deepen our knowledge of the cosmos and bring it closer to society. For this, the IAA conducts cutting-edge Astrophysical and Space Science research, promotes technological development through the construction of new instrumentation and disseminates their research among the scientific community and the public in general through science communication activities.

About CAB-INTA-CSIC

The Centro de Astrobiología (CAB) is a joint research center of INTA and CSIC. Created in 1999, it was the first center in the world dedicated specifically to astrobiological research and the first non-American center associated with the NASA Astrobiology Institute (NAI), currently the NASA Astrobiology Program. It is a multidisciplinary center whose main objective is to study the origin, presence and influence of life in the universe through a transdisciplinary approach. CAB was distinguished in 2017 by the Ministry of Science and Innovation as a “María de Maeztu” Unit of Excellence.