Astronomers have seen for the first time how a supermassive black hole stopped star formation in its galaxy

The process of star formation inhibition is an important aspect of the evolution of galaxies, which is why scientists are so eager to understand it. According to the results of cosmological computer models, active galactic nuclei are to blame. These matter-absorbing supermassive black holes are theoretically capable of “blowing” cold gas out of the interstellar space surrounding them with their activity.

The fact is that when a black hole absorbs a lot of matter, an accretion disk forms around it, in which matter spins at enormous speed. From the friction of particles against each other, the matter in the disk heats up to enormous temperatures and begins to radiate, greatly heating the gas in the regions adjacent to such an active center of the galaxy. From this radiation, interstellar gas begins to fly apart.

Thanks to large-scale surveys of galaxies, astronomers have begun to find signs of gas movement in them. The problem is that what was observed was mostly ionized, that is, heated, gas. Calculations have shown that such “blowing” is unlikely to interrupt star formation. Only in the case of extremely active galactic nuclei did scientists see a connection with the inhibition of the birth of new stars. Meanwhile, in the young Universe there are many galaxies with extinct star formation.

In a new work published in the journal Nature, astronomers have described a galaxy in which a normal active galactic nucleus is blowing out enough cold and hot gas to inhibit star formation. Thus, for the first time, they directly confirmed hypotheses and theoretical calculations.

Observations of not only ionized, but also cold interstellar gas became possible thanks to the James Webb Space Telescope. As part of the Blue Jay survey, the telescope observed more than 150 galaxies in the early Universe at redshifts ranging from 1.7 to 3.5. This means that the light from these galaxies took from 9.86 to 11.9 billion years to reach us. Of these, 17 objects turned out to be “extinct,” including the galaxy COSMOS-11142.

In addition to the many emission lines of warm ionized gas, the James Webb detected three absorption lines: ionized calcium (Ca II K and Ca II H) and sodium (Na ID). Absorption along these lines indicates the presence of cold gas. The analysis revealed a blue shift of both some emission and absorption lines, that is, part of the gas is moving not away from us, but towards us – a clear sign of “blowing.” If you combine all the observational data, you get an “inflating bubble”, because the gas movement is both “behind” and “in front” of the center of the galaxy.

Based on the ratio of elements and the rate of “inflation” of ionized gas, scientists concluded that the cause of this movement can only be an active galactic nucleus. The “blowing out” of cold gas is slower, but the volumes are amazing. If in ionized gas the galaxy loses less than one solar mass per Earth year, then in cold gas it loses 35 solar masses per Earth year. It turns out that ionized gas makes up only a small part of the total loss.

The following scenario emerges: the peak of star formation in the galaxy COSMOS-11142 ended 300 million years before the stage that we are now observing. By the time of observations, the rate of star formation in it had dropped by two orders of magnitude, that is, hundreds of times. The galaxy now produces between one and 10 solar masses per year. The study authors suggested that COSMOS-11142 is in the middle of a “braking” process.

The main conclusion of the new work is different. The galaxy COSMOS-11142 was not included in the X-ray and radio surveys. That’s because they are determined to look for the brightest active galactic nuclei and star-forming galaxies.

It turns out that a powerful “blowing out” of cold gas can occur in most massive galaxies of the young Universe; existing X-ray and radio instruments simply lack the sensitivity to detect it. Fortunately, according to Rebecca Davis, one of the authors of the study, previously astronomers “saw” only one percent of the “blown” gas, but with the help of James Webb it is now possible to see and analyze much more.