NASA’s Hubble Space Telescope and the Chandra X-ray Observatory have detected a pair of supermassive black holes in tight proximity. In colliding galaxies, black holes at their centers pull in gas and dust, making them shine brightly as active galactic nuclei (AGN). This AGN pair is detected in MCG-03-34-64.
Both black holes are 300 light-years apart from each other. While many “dual” black holes have been found before, they are usually much farther apart than the ones discovered in the gas-rich galaxy MCG-03-34-64.
This type of AGN is frequently found in the early universe when galaxy mergers were more frequent. This study offers a unique close-up look at a nearby example, located about 800 million light-years away.
The discovery was unexpected. Hubble’s high-resolution images showed three optical diffraction spikes inside the host galaxy, pointing to a dense cluster of glowing oxygen gas in a tiny region.
Anna Trindade Falcão of the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts said, “We were not expecting to see something like this. This view is not a common occurrence in the nearby universe, and told us something else is happening inside the galaxy.”
When light from a tiny region bends around a telescope’s mirror, it causes diffraction spikes.
The team then used the Chandra observatory to investigate. When they looked at MCG-03-34-64 in the X-ray band, they saw two separated, powerful sources of high-energy emission coincident with the bright optical points of light seen with Hubble.
Falcão said, “We put these pieces together and concluded that we were likely looking at two closely spaced supermassive black holes.”
Scientists supported their interpretation using archival radio data from the Karl G. Jansky Very Large Array near Socorro, New Mexico. This black hole pair also emits powerful radio waves.
Falcão said, “When you see a bright light in optical, X-rays, and radio wavelengths, many things can be ruled out, leaving the conclusion these can only be explained as close black holes. Putting all the pieces together gives you the picture of the AGN duo.”
The third bright light source seen by Hubble is unknown and needs further study. It could be gas shocked by energy from a jet of fast-moving plasma from one of the black holes, similar to how a garden hose blasts water into sand.
“We wouldn’t be able to see all of these intricacies without Hubble’s amazing resolution,” said Falcão.
Both black holes were once at the core of their respective host galaxies. A merger between the galaxies brought the black holes into close proximity.
Journal Reference:
- Anna Trindade Falcão, T. J. Turner et al. Resolving a Candidate Dual Active Galactic Nucleus with ∼100 pc Separation in MCG-03-34-64. The Astrophysical Journal. DOI 10.3847/1538-4357/ad6b91
