Astronomers from the University of Arizona (UA) and other countries report the discovery of a new ultra-weak dwarf galaxy. The newly discovered galaxy, called Tucana B, is the first extinct and isolated object of this type to be found on the far outskirts of the Local Group. This was reported in an article published on May 18 on the pre-print server arXiv.
The so-called ultra-weak dwarf galaxies (UFD) are the least bright galaxies with the greatest predominance of dark matter and the least chemically developed galaxies. Therefore, they are perceived astronomers as the best candidate of fossils from the universe in its early stages.
Now a team of researchers led by David J. Sanda from UA found a new UFD during a visual search for weak dwarf galaxies satellites of the distant dwarf spherical galaxy Toucan. They used data from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and their interactive viewing of color images.
“We uploaded a custom file to mark an area with a projected radius of 100 kpc (≈6.4 degrees at a distance from Toucan) and looked for a visual excess density of untied stars with major diffused lightindicating a dwarf galaxy on the edge of the Local Group. The field was surveyed at different spatial scales and contrast levels. The Tucana B stood out during the search and partially split into stars in the Legacy Imaging Survey program, ”the astronomers explained.
According to the document, Tucana B is approximately 6 degrees from the dwarf sphere of Tucana and is approximately 1.6 million light years further in line of sight. It is estimated that the distance to Toucan B from Earth is about 4.5 million light years.
Tucana B has a half-light radius of about 260 light-years and an absolute magnitude of -6.9 mag, making it comparable to the ultra-weak satellite galaxies of the Milky Way. UFD seems to consist only of old poor metal stellar populations.
Astronomers have noted that the luminosity of Tucana B and the obvious absence star formation as well as neutral gas make it unique among recent discoveries at this approximate distance. Moreover, the extraordinary isolation of Tucana B may indicate that its star formation was stopped by reionization or some other internal mechanism rather than interaction with the halo of a larger galaxy.
The Sanda team views Tucana B as an excellent target for future space observations aimed at elucidating its structure and the history of star formation, possibly right up to the oldest turn of the main sequence.
“In particular, Tucana B may provide a definitive opportunity to understand the role that regionalization plays in extinguishing the weakest galaxies,” the researchers concluded.
They added that finding more facilities, such as Tucana B, is needed to better understand the population demographics of the UFD field.
DJ Sand et al, Tucana B: Isolated and extinguished ultra-weak dwarf galaxy with D = 1.4 Mpc. arXiv: 2205.09129v1 [astro-ph.GA], arxiv.org/abs/2205.09129
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Citation: A new ultra-weak dwarf galaxy has been discovered (May 26, 2022), received on May 26, 2022 from https://phys.org/news/2022-05-ultra-faint-dwarf-galaxy.html
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