This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Nearly every galaxy has a supermassive black hole. The few that don't have had theirs ejected during a galactic collision.
That's because galaxies and their black holes have formed hand in hand. There is still some debate as to whether galaxies formed around the seeds of supermassive black holes or the other way around, but there is plenty of evidence to support the idea that the two evolve together. One point of evidence is the fact that supermassive black holes generally have about 0.5% of a galaxy's mass.
The mass correlation between black holes and galaxies suggests a strong connection in how they form. In the same way, the correlation between the size of a city and the number of people who live there suggests a connection between structural size and population. But a recent study found oversized galactic black holes, challenging our understanding of their evolution.
For this study, published in Astronomy & Astrophysics, the team used the eROSITA X-ray telescope and other observations to look at more than 20,000 quasars. Quasars are powered by active supermassive black holes. As the black holes consume nearby material, they emit a tremendous amount of light, such as X-rays and radio waves.
The intensity of a quasar is related to the mass of the black hole, so quasars are a great way to study the distribution of black hole masses. For many quasars, we also know the mass of their galaxies. By observing the region of a quasar in visible and infrared light, we can determine the brightness of the galaxy, which is proportional to its mass.
When the team compared galaxy masses with the masses of their black holes, eight quasars stood out. Rather than the usual mass ratio of 200 to 1, these systems had a ratio of 20 to 1. In other words, the mass of these black holes makes up about 5% of the galaxy's mass.
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