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The biggest black holes are growing faster than the rate of stars being formed in their galaxies, in accordance with two new studies using data from NASA’s Chandra X-ray Observatory and other telescopes. More than many years, astronomers have collected data on the arrangement of stars in galaxies and the growth of the biggest black holes (that is, those with millions or billions the mass of the Sun) in their centers. Now, results from two independent groups of researchers point out that the black holes in massive galaxies have grown much faster than in the less massive ones.
“We are trying to reconstruct a race that started billions of years ago,” thought Guang Yang of Penn State who led one of the two studies. “We are using extraordinary data taken from different telescopes to figure out how this cosmic competition unfolded.”
The scientists intended the relation between the biggest black hole’s growth rate and the growth rate of stars in its host galaxy. A common idea is that this relation is about constant for all galaxies. As an alternative, Yang and colleagues found that this relation is much higher for more massive galaxies. For galaxies containing about 100 billion solar masses worth of stars, the relation is about ten times higher than it is for galaxies containing about 10 billion solar masses worth of stars. “An evident question is why? Maybe massive galaxies are more effective at feeding cold gas to their central the biggest black holes than less massive ones.” said co-author Niel Brandt.
Mezcua indicated “We found black holes that are far the bigger than we expected, maybe they got a head start in this race to grow, or maybe they’ve had an edge in speed of growth that’s lasted billions of years.” The researchers shown that almost half of the black holes in their example had masses estimated to be at least 10 billion times the mass of the Sun. This places them in an extreme weight category that some astronomers call “ultramassive” black holes.
The work by Mezcua was published in the February 2018 issue of Monthly Notices of the Royal Astronomical Society.