Astronomers using the Gemini North telescope have found the remnants of 106 galaxies as they transition into ultra-compact dwarf galaxies.
Ultra-compact dwarf galaxies (UCDs) are among the densest stellar groupings in the Universe.
Being more compact than other galaxies with similar mass, but larger than star clusters — the objects they most closely resemble — these mystifying objects have defied classification.
The idea that UCDs are remnants of disrupted dwarf galaxies has been proposed since they were discovered over two decades ago.
However, previous searches have not revealed the large population of galaxies-in-transition that you would expect to find.
So Peking University astronomer Kaixiang Wang and colleagues conducted a systematic search for these objects around the Virgo Cluster, a group of about 1,300 — and possibly up to 2,000 — member galaxies in the direction of the constellation of Virgo.
Using the Gemini North telescope, they identified 106 of these missing-link galaxies that show every stage of the transformation process.
“Our results provide the most complete picture of the origin of this mysterious class of galaxy that was discovered nearly 25 years ago,” said NOIRLab astronomer Eric Peng.
“Here we show that 106 small galaxies in the Virgo cluster have sizes between normal dwarf galaxies and UCDs, revealing a continuum that fills the ‘size gap’ between star clusters and galaxies.”
The astronomers compiled their sample by first looking at images from the Next Generation Virgo Cluster Survey, taken with the Canada-France-Hawai’i Telescope.
And though they were able to identify hundreds of candidate UCD progenitors, they were unable to confirm their true nature.
The obstacle was that UCDs that are surrounded by envelopes of stars are indistinguishable from normal galaxies that are located farther away beyond the Virgo Cluster.
To distinguish the candidate UCD progenitors from the background galaxies, the researchers…
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