A new study describes the misidentification of 28 supermassive black holes, found approximately 5 billion light-years away within the Chandra Deep Field-South.
A team of researchers led by Erini Lambrides of Johns Hopkins University spotted the black holes which have been there all along but masqueraded as other cosmic objects. The team had used NASA's Chandra X-ray Observatory and a host of other telescopes, including the Spitzer Space Telescope and Hubble Space Telescope.
"With our new identifications we've found a bunch of heavily obscured black holes that had previously been missed," Lambrides said in a statement. "We like to say we found these giant black holes, but they were really there all along."
Within this image, astronomers had already identified 67 black holes that have been obscured by envelopes of gas and dust, creating a cocoon-like structure. Now, with this new study, researchers have identified these 28 supermassive black holes, which were previously miscategorized as either slowly growing black holes with low-densities or without cocoons or distant galaxies.
The new observations paved the way to the realization that the objects were actually supermassive black holes, the biggest type of black hole that grows by sucking in any surrounding material using their extremely powerful gravitational pull. Material pulled in by the black hole builds up heat and produces radiation in different wavelengths, including X-rays. This is why the use of X-ray telescopes are critical in observing these cosmic objects.
Lambrides and her team came to this conclusion by comparing their data with what is expected for a growing black hole then predicted the number of X-rays that each object emits. 28 X-ray sources were found to have a much lower level, leading them to discover the cocoon of dust and gas surrounding the objects is about 10 times denser than their previous calculations.
With the higher-density cocoon considered, the team was able to show how these black holes emit more X-rays than previously believed, given that the cocoon inhibits a huge amount of radiation from going out and being observed from our planet. As these cocoons feed growing black holes, finding that these cocoons are much denser than expected led the researchers to find that the black holes are growing quickly as they are fueled by these surrounding envelopes.
The findings are of huge importance because it supports theoretical models that measure how many black holes exist in the universe, the rate of their growth, and what's possibly hiding them and changing how they are seen from our end.
The paper has been published in The Astrophysical Journal in June.
