ESA / Gaia / DPAC; SDSS
Burako Negro – Leo I.
Astronomers at the University of Texas’ MacDonald Observatory at Austin have discovered an unusually massive black hole at the center of one of the Milky Way’s dwarf satellite galaxies, named Leo I.
This discovery, almost as massive as a black hole in our galaxy, could redefine our understanding of how all galaxies – the building blocks of the universe – evolve. work was published by in a recent issue of the Astrophysical Journal.
The team decided to study Leo I am because of its peculiarity. Unlike most dwarf galaxies orbiting the Milky Way, Leo I does not contain much dark matter.
investigators measured the profile of dark matter Leo I – That is, how the density of dark matter changes from the outer edges of the galaxy towards the center.
They did this by measuring their gravitational attraction towards the stars: the faster the stars move, the more matter is trapped in their orbits. Specifically, the team wanted to know if the density of dark matter is increasing towards the center of the galaxy.
They also wanted to know if their profile would be measured. compatible with previous received using data from old telescopes in combination with computer models.
The team, led by the recent Ph.D. from the University of Texas at Austin, Maria Jose Bustamante, includes astronomers Eva Noyola, Karl Gebhardt and Greg Seimann from the same institution, as well as colleagues from the Max Planck Institute for Extraterrestrial Physics in Germany.
For their observations, they used a unique instrument called VIRUS-W, mounted on the 2.7-meter Harlan J. Smith telescope located at the MacDonald Observatory.
When the team submitted their augmented data and complex models in a supercomputer at the University of Texas Advanced Computing Center at Austin, got an amazing result.
“Models are screaming that we need a black hole in the center; we really don’t need a lot of dark matter, ”Gebhardt said. “We have a very small galaxy that is falling into the Milky Way, and its black hole is almost as massive as the Milky Way.… The mass ratio is absolutely enormous. The Milky Way dominates; the black hole of Leo I is almost comparable. ” The result is unprecedented.
The researchers said the result was different from previous Leo I studies due to a combination of more accurate data and better simulations on a supercomputer.
Dense central region of the galaxy remained practically unknown in previous studies that focused on the speed of individual stars. Current research has shown that for the few speeds obtained in the past, there was a bias towards lower speeds. This, in turn, reduced the estimated amount of matter trapped in their orbits.
New data are concentrated in the central region and are not subject to this bias. The amount of putative matter trapped in the orbits of stars has skyrocketed.
The discovery could undermine astronomers’ understanding of galactic evolution because “there is no explanation for this type of black hole in dwarf spheroidal galaxies, ”said Bustamante.
The result is even more important because astronomers have used galaxies like Leo I to be classified as galaxies. “dwarf spheroidal galaxy”“20 years ago to understand how dark matter is distributed in galaxies,” added Gebhardt. This new type of black hole fusion is also giving gravitational wave observatories a new signal to watch out for.
“If the mass of a Leo I black hole is large, that could explain how black holes grow in massive galaxies,” Gebhardt said. This is because over time, as small galaxies like Leo I fall into larger galaxies, the black hole of the smaller galaxy merges with the black hole of the larger galaxy, increasing its mass.
Created by a team from the Institute for Extraterrestrial Physics. Max Planck in Germany, the VIRUS-W is the only device in the world capable of currently performing studies of dark matter profiles of this type.
Noyola noted that many of the dwarf galaxies observed from the southern hemisphere are good candidates, but no telescope in the southern hemisphere is equipped for this. However, the GMT (Giant Magellanic Telescope) currently under construction in Chile was partly designed for this kind of work. The University of Texas at Austin is a Founding Partner of GMT.