Black Holes Have an Effect on How Entire Galaxies

The graph shows an extremely massive black hole surrounded by a dust ring (torus). The incidence of gas onto the black hole leads to a high-energy beam of matter and radiation, which can be transported over cosmological distances. If the beam is shown in our direction, we speak of a “blazar.”

The influence of extremely massive black holes is limited, cosmic seen on its immediate environment – is so at least the previous assumption. An international team of astronomers has now discovered, however, that these black holes of millions to billions of solar masses also affects much more distant objects, and subsequently even may have on the formation of galaxies. The researchers from Germany, Canada and the United States observed that diffuse gas absorbs the light in space gamma radiation from black holes and heats it. This surprising finding has important implications for the formation of large structures in the universe.

In the center of every galaxy is an extremely massive black hole. It can emit high-energy gamma radiation and is then called blazar. Other types of radiation such as visible light or radio waves passing through the universe without any problems. This is true for high-energy gamma radiation is not. This radiation interacts with the optical light emitted by the galaxies, and is converted into the elementary particles, electrons and positrons. The elementary move initially nearly light speed, but slowed down by the diffuse gas in the universe. Since each braking process generates heat, the surrounding gas heats it to extreme. It is ten times hotter on average and in the cosmic regions with less density than the average even more than a hundred times hotter than previously thought.

Temperature measurement in the line of forest

“Blazars, the thermal history of the universe to write,” said Christoph Pfrommer, one of the authors, from the Heidelberg Institute for Theoretical Studies (HITS). But how can you verify such an idea? In the optical spectra of distant quasars seen a number of lines, the so-called forest line. The forest is created by absorption of ultra-violet quasar by neutral hydrogen atoms in the early stages of the universe. If the gas is now hot, then the weakest lines are widened. This effect produces a great way to measure temperature in the early universe and thus virtually to observe the universe in his youth.

The HITS-examined Astrophysicists this newly postulated heating process for the first time with detailed computer simulations of the cosmological origin of structures. Surprisingly, the lines were just so broadened that they exactly match the measured line in the quasar spectra match statistics. “We can solve elegantly a long standing problem with these Quasardaten” says Ewald fixed Puchwein who performed the simulations on the mainframe at the HITS.

The impact on galaxy formation

What other consequences resulting from this new source of heat? The forest line in the quasar spectra is caused by density fluctuations in the universe. Here, the densest fluctuations fall together over time to form galaxies and galaxy clusters, as we see around us. If the diffuse gas is too hot, it can not collapse and the formation of dwarf galaxies is delayed or even completely suppressed. This could be the key to the solution of another problem in the theory of galaxy formation are that there has long been: Why are close to our Milky Way and in dense cosmic regions observed significantly fewer dwarf galaxies than predicted by cosmological simulations?

Volker Springel, head of research group at HITS, said: “The most exciting of the new process is the Blazarheizens that this same effect can explain several puzzles in the cosmological structure formation.” The group now plans to further refine the simulation models and to understand so the physical nature of blazars and their impact on today’s universe better.