A galaxy containing an active galactic nucleus (AGN) is one in which matter is falling toward the supermassive black hole at its center, releasing enormous amounts of energy. Some AGNs emit part of this energy in the form of jets or jets detectable at radio wavelengths (radiojets) that travel at relativistic speeds (close to that of light and which, therefore, already manifest detectable effects over space. -time). As the ejecta propagates through the galaxy, it collides with surrounding clouds and gas and, in some cases, pushes this material away as winds. However, knowledge about the conditions that favor the emanation of winds in galaxies has been scarce.
The effect of the jets on the stars, dust and gas contained in galaxies plays a relevant role in the evolution of galaxies in the universe. The most powerful radiojets, housed in radio-intense active galaxies, can drastically change the fate of galaxies by heating up the gas, preventing the formation of new stars and halting galactic growth. Computer simulations predict that relativistic jets bursting into a disk-shaped galaxy alter the distribution of gas, dispersing it into bubbles as they spread through the galaxy. One of the key elements for these ejections to be effective in the emission of winds is the angle between the gaseous disk and the propagation of the jet. Surprisingly, less powerful jets, such as those from so-called radio-silent galaxies, are capable of producing more changes in the surrounding medium than very powerful ones.
An international scientific team, led by Anelise Audibert, a researcher at the Instituto de Astrofísica de Canarias (IAC), discovered a perfect case to study the interaction of a radiojet with the cold gas surrounding a massive quasar: the Teacup galaxy. A radio-silent quasar located 1.3 billion light-years away, its nickname comes from the expanding bubbles seen in visible light and radio, one of which forms a bulge resembling the handle of a teacup. . In addition, the central region (about 3,300 light-years in size) harbors a young, compact radiojet that is slightly tilted with respect to the galaxy’s disk.
Effects on star formation
Through observations made in the Chilean desert with the ALMA observatory (Atacama Large Millimeter/submillimeter Array), the team was able to capture the presence of dense and cold gas in the central part of the Teacup galaxy. In particular, the astronomers detected the emission of carbon monoxide molecules that can only exist under certain conditions of density and temperature. Based on these observations, the team found that the compact jet, despite being low-powered, is not only clearly disturbing the distribution of the gas and heating it, but also accelerating it in an unusual way.
The team hoped to detect these extreme conditions in the impacted regions along the jet, but when they analyzed the observations, they found that this gas is turbulent and hotter in the direction perpendicular to the jet’s propagation direction. “This is due to the interaction of the bubble produced by the jet with the surrounding gas, which it heats and disperses as it expands laterally,” explains Audibert. “Based on comparison with computer simulations, we believe that the orientation between the cold disk and the jet is a crucial factor in effectively driving these crosswinds,” he adds.
A compact radiojet at the center of the Teacup Galaxy produces a turbulent crosswind in the cold gas, just as the simulations predict. (Images: HST / ALMA / VLA / M. Meenakshi / D. Mukherjee / A. Audibert. CC BY)
“Low-powered jets were previously thought to have a negligible impact on the galaxy, but work like ours shows that, even in the case of radio-quiet galaxies, the jet is redistributing and perturbing the gas around it, which will have associated with an impact on the galaxy’s ability to form new stars,” says Cristina Ramos Almeida, a researcher at the IAC and co-author of the study.
The next step is to observe a larger sample of radiosilent quasars with MEGARA, an instrument installed on the Gran Telescopio CANARIAS (GTC). The observations will help to understand the impact of the jets on the faintest and hottest gas, and to measure the changes in star formation caused by the winds. This is one of the objectives of the QSOFEED project, developed by an international scientific team led by Cristina Ramos Almeida and dedicated to investigating how the winds from supermassive black holes affect the galaxies that host them.
The study is titled “Jet-induced molecular gas excitation and turbulence in the Teacup”. And it has been published in the academic journal Astronomy and Astrophysics. (Source: IAC)