Chandra Observes Gravitationally-Lensed Supermassive Black Hole System

By combining gravitational lensing with the capabilities of NASA’s Chandra X-ray Observatory, astronomers have detected two X-ray-emitting objects — two growing supermassive black holes or one such black hole and a jet — in an active galaxy called MG B2016+112. The X-rays detected by Chandra were emitted by MG B2016+112 when the Universe was only 2 billion years old.

MG B2016+112: the X-ray light from one of the objects on the left (purple) has been warped by the gravity of the intervening galaxy to produce two beams and X-ray sources (A and B) detected in the Chandra image, which is represented by the dashed square on the right; the X-ray light from the fainter object (blue) produces an X-ray source (C) that has been amplified by the galaxy to be as much as 300 times brighter than it would have been without the lensing; the Chandra image is shown in the inset; these two X-ray-emitting objects are likely a pair of growing supermassive black holes or a growing supermassive black hole and a jet. Image credit: NASA / CXC / M. Weiss / SAO / Schwartz et al.

MG B2016+112: the X-ray light from one of the objects on the left (purple) has been warped by the gravity of the intervening galaxy to produce two beams and X-ray sources (A and B) detected in the Chandra image, which is represented by the dashed square on the right; the X-ray light from the fainter object (blue) produces an X-ray source (C) that has been amplified by the galaxy to be as much as 300 times brighter than it would have been without the lensing; the Chandra image is shown in the inset; these two X-ray-emitting objects are likely a pair of growing supermassive black holes or a growing supermassive black hole and a jet. Image credit: NASA / CXC / M. Weiss / SAO / Schwartz et al.

The X-ray emission from inner regions of active galaxies is a key to our understanding of supermassive black hole growth, mergers, and accretion processes.

However, the study of formation of galaxies in the early Universe is limited by the inability of telescopes to detect and resolve inner regions of these faint objects.

At high energies, physical constraints limit further improvements of the resolution of telescopes.

As a result, present and future missions will not provide sufficient resolution to resolve inner regions of merging galaxies potentially hosting multiple active galactic nuclei.

“Our efforts to see and understand such distant objects in X-rays would be doomed if we didn’t have a natural magnifying glass like this,” said Dr. Dan Schwartz, an astronomer at the Harvard & Smithsonian Center for Astrophysics.

Using radio observations of MG B2016+112, astronomers previously found evidence for a pair of rapidly growing supermassive black holes separated by only about 650 light-years. Both of the black hole candidates possibly have jets.

In the new study, Dr. Schwartz and colleagues concluded that the three X-ray sources in the MG B2016+112 system must have resulted from the lensing of two distinct objects.

These two X-ray-emitting objects are likely a pair of growing supermassive black holes or a growing supermassive black hole and its jet.

The estimated separation of these two objects is consistent with the radio work.

“Astronomers have discovered black holes with masses billions of times greater than that of our Sun being formed just hundreds of millions of years after the Big Bang, when the Universe was only a few percent of its current age,” said Dr. Cristiana Spingola, an astronomer at the Italian National Institute for Astrophysics.

“We want to solve the mystery of how these supermassive black holes gained mass so quickly.”

The uncertainty in the X-ray position of one of the objects in MG B2016+112 is 130 light-years in one dimension and 2,000 light-years in the other, perpendicular dimension.

This means that the size of the area where the source is likely located is more than 100 times smaller than the corresponding area for a typical Chandra source that is not lensed.

Such precision in a position determination is unparalleled in X-ray astronomy for a source at this distance.

“Thanks to gravitational lensing much longer Chandra observations may be able to distinguish between the black hole pair and the black hole plus jet explanations,” Dr. Schwartz said.

“We also look forward to applying this technique in the future, especially as surveys by major new optical and radio facilities that will soon come on line will supply tens of thousands of targets.”

“Without this effect Chandra would have had to observe it a few hundred times longer and even then would not reveal the complex structures,” said Dr. Anna Barnacka, an astronomer at the Harvard & Smithsonian Center for Astrophysics and Jagiellonian University.

The team’s paper was published in the Astrophysical Journal.

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Daniel Schwartz et al. 2021. Resolving Complex Inner X-Ray Structure of the Gravitationally Lensed AGN MG B2016+112. ApJ 917, 26; doi: 10.3847/1538-4357/ac0909

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