According to observations and cosmological simulations, dwarf galaxies are the most abundant type of galaxies in the early Universe and the galaxy merger rate is dominated by dwarfs. However, these mergers are generally too distant to be directly observed, and dwarf-dwarf galaxy merger-related pairs of supermassive black holes are notoriously hard to find. In a new paper in the Astrophysical Journal, astronomers from the University of Alabama at Tuscaloosa present the first results of large-scale search for this elusive type of object and the first two candidates for dual supermassive black holes in dwarf-dwarf mergers. The dwarf galaxies detected by the researchers are on collision courses and are found in the galaxy clusters Abell 133 and Abell 1758S.
Galaxies are made up of billions of stars, interstellar gas and dust, and large amounts of dark matter.
Every (or almost every) galaxy is expected to host a supermassive black hole in its center.
Galaxies and their central black holes grow and evolve together predominantly through mergers; smaller objects merge to create larger ones over time. However, the earliest stages of galaxy evolution involving the mergers of the first galaxies are poorly understood.
It is unclear how the first mergers affected the morphology of ancient galaxies and their star formation.
Astronomers also do not know how massive the first black holes were that inhabited the first galaxies, nor how the first mergers influenced their ability to accrete material.
It is challenging to answer these important questions because the first mergers are too distant and faint to be directly observed.
One way to overcome this issue is to look for local analogs. In other words, scientists need to find pairs of small, dwarf galaxies that have had very quiet lives, with almost no mergers, that have only recently met and started interacting.
Such galaxies have experienced little to no evolution so they are analogs of distant, ancient galaxies, and…
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