Giant black holes discovered on a collision course in a dwarf galaxy

Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Micic et al.; Optics: International Gemini Observatory/NOIRLab/NSF/AURA Press image, caption and videos.

A new study conducted with NASA’s Chandra X-ray Observatory has tracked two pairs of supermassive black holes in colliding dwarf galaxies. This is the first hint of such an upcoming encounter, providing scientists with crucial insights into the growth of black holes in the early Universe.

Es bien sabido que las galaxias enanas se fusionan para crecer hasta convertirse en las galaxias más grandes que se ven hoy en día. Sin embargo, la tecnología actual no permite observar la primera generación de fusiones de galaxias enanas porque son extraordinariamente débiles a grandes distancias.

The current study overcame these hurdles by using a systematic scan of deep X-ray observations from Chandra and combining them with optical data from the Canada-France-Hawaii Telescope and infrared data from NASA’s Wide Infrared Survey Explorer (WISE) (CFHT).

The team searched for pairs of bright X-ray sources in colliding dwarf galaxies for evidence of the existence of two black holes and discovered two examples.

The composite image on the left shows a pair in the galaxy cluster Abell 133, 760 million light-years from Earth. Pink color represents Chandra X-ray data, while blue represents CFHT optical data. This pair of dwarf galaxies shows a long tail due to the tidal effects of the collision and appears to be in the late stages of merging.

The authors of the present study have given it the nickname “Mirabilis” after a critically endangered hummingbird species known for having unusually long tails. Due to the almost complete merger of two galaxies into one, only one name was chosen. In each galaxy, the two Chandra sources show X-rays coming from the region surrounding the black holes.

The other pair was discovered in Abell 1758S, a galaxy cluster located about 3.2 billion light-years away.

The researchers named the merging dwarf galaxies “Elstir” and “Vinteuil,” after the fictional artists of Marcel Proust’s “In Search of Lost Time.” The galaxy at the top is called Vinteuil, and the one at the bottom, Elstir.

According to scientists, these two have been trapped in the early stages of a merger, which has caused a bridge of stars and gas to connect the two colliding galaxies through their gravitational interaction. Follow-up observations of these two systems will allow astronomers to study processes crucial to understanding galaxies and their black holes in the very early stages of the Universe.

Sources, credits and references:

NASA – Marko Mićić et al, Two Candidates for Dual AGN in Dwarf-Dwarf Galaxy Mergers, arXiv (2022). DOI: 10.48550/arxiv.2211.04609