by The history of galaxies’ dark cores has been told almost entirely for the first time, as astronomers combine X-ray observations with supercomputer models to describe the galaxies’ growth. supermassive black holes over 12 billion years of cosmic history.
In doing so, scientists have shown that the black hole is at our core The Milky Way Galaxy it reached four million solar masses relatively late in its history.
The range of supermassive black holes is millions of times larger than it used to be our sun billions of times larger, but their origin is unclear and it has been a challenge for astronomers to understand how they grew to such huge masses.
Now, however, astronomers Fan Zou and W. Niel Brandt, both of Penn State University, are leading a team that has linked the two black hole growth mechanisms from observations and simulations. The results may finally provide some answers.
Related: NASA telescope sees ‘cosmic fireworks’ and faint echoes from Milky Way’s supermassive black hole
“A big question is how do these supermassive black holes grow so massive?” Zou said as he presenting their work at the 244th meeting of the American Astronomical Society in Wisconsin.. “To address that, we need to trace the overall growth history of these supermassive black holes.”
As mentioned, black holes grow through two main mechanisms. One is by accreting cold gas from its host galaxy. This gas forms an accretion disk around the black hole itself and material from the disk gradually moves towards the black hole’s core. The accretion disk can grow so dense that friction between gas molecules causes heat up to millions of degrees, radiating X-rays in the process. The other mechanism occurs during galaxy collisions. When this happens, not only do galaxies merge, but their supermassive black holes eventually merge and release a burst of gravitational waves.
Cosmic emptiness tracking
To assess the contribution of gas accretion to the growth of supermassive black holes, the study team combed through more than 20 years of archival data from NASAand Chandra X-ray ObservatoryEuropean Space Agency XMM- Newton mission and the eROSITA X-ray instrument on board the German-Russian joint Spektr-RG spaceship. The researchers were able to identify X-ray signals coming from about 8,000 rapidly growing supermassive black holes.
“When supermassive black holes accrete the surrounding gas they emit strong X-rays, so by detecting them in the X-ray bands we can measure their accretion power,” said Zou.
They then went to the IllustrisTNG cosmological a supercomputer simulation to model galaxy mergers throughout cosmic history. From there, the team combined X-ray data showing growth by accretion with the results of simulated mergers to understand how and when supermassive black holes grew over the past 12 billion years, from 1.8 billion years after the. Big bang to this day.
These simulations “capture the overall large-scale structure [of the universe] but they are also able to explore individual galaxies,” Zou said.
Amazing black hole stories
Zou and Brandt found that the X-ray data show that accretion is the main driver of black hole growth during all periods of cosmic history. Furthermore, the more massive the galaxy, the faster the supermassive black hole inside grew due to accretion. Mergers, on the other hand, are not the same black hole growth according to the simulations, but there may still be some impact.
“Accreditation leads the massive black hole growth in most cases and mergers make some significant secondary contributions,” Zou said.
These results also show that supermassive black holes grew more rapidly earlier in the universe, with new ones appearing frequently. By about 7 billion years ago, however, the total number of supermassive black holes was more or less fixed and very few new supermassive black holes formed. Mergers became more influential in later history, peaking in importance for the growth of a black hole about 4 billion years ago.
“We found that once the universe reaches about 40% of its age, the overall demography of supermassive black holes is very similar to the demography of supermassive black holes we see in the local universe,” Zou said.
Astronomers even specifically modeled our galaxy’s black hole, Sagittarius A*and he concluded that most of his material grew relatively late in life time. This growth has been largely through accretion, with most mergers of the Milky Way with other galaxies occurring more than 8 billion to 10 billion years ago. However, the European Space Agencyand Gaia mission yes recently received evidence your dwarf galaxy collided with the Milky Way just 2 billion to 3 billion years ago. Agar galaxies are thought to contain medium-sized black holes, measuring thousands to hundreds of thousands of the mass of our sun, and it is possible that one could merge with Sagittarius A* to increase the mass of our black hole.
Related Stories:
— Hubble Telescope maps high-speed ‘burps’ from nearby supermassive black hole for 1st time
— The heaviest black hole pair ever observed weighs 28 billion times that of the sun
— Why are supermassive black hole jets so short? Astronomers may have cracked the case
Because the results only take us back to 1.8 billion years after the Big Bang, they do not describe how the seeds for supermassive black holes first formed. This is still a quandary for cosmologists, especially as the Hubble Space Telescope and the James Webb Space Telescope got surprisingly massive black holes earlier in the history of the universe. How they grew to be millions of times the mass of our sun in less than a billion years is currently unknown.
One paper describing the results was published in March i The Astrophysical Journalwith a second paper waiting in the pipeline.
