A new ultra-faint dwarf galaxy has been discovered, according to astronomers from the University of Arizona (UA) and other institutions. Tucana B, the newly discovered galaxy, is the first quenched and isolated object of this type discovered on the fringes of the Local Group. The findings were published on the arXiv pre-print server on May 18th.
The so-called ultra-faint dwarf galaxies (UFDs) are the most chemically developed, least bright, and dark-matter-dominated galaxies known. As a result, astronomers consider them to be the best potential fossils from the early stages of the cosmos.
Now, during a visual search for dim dwarf galaxy companions to the distant dwarf spheroidal galaxy Tucana, a team of researchers led by UA’s David J. Sand has discovered a new UFD. They used data from the Legacy Imaging Surveys Data Release 9 of the Dark Energy Spectroscopic Instrument (DESI) and their interactive colour image viewer.
“We used a custom file to define a region with a projected radius of 100 kpc (6.4 deg at Tucana’s distance) and looked for visual over-densities of resolved stars with underlying diffuse light, which could indicate a dwarf galaxy at the Local Group’s border.
A range of geographic sizes and contrast levels were used to examine the field. Tucana B shone out throughout the search, and in the Legacy Imaging Survey viewer, it is partially resolved into stars “The astronomers explained their findings.
Tucana B is around 6 degrees away from the Tucana dwarf spheroidal, and is about 1.6 million light years away along the line of sight, according to the paper. Tucana B is about 4.5 million light years away from Earth, according to calculations.
Tucana B has a half-light radius of 260 light-years and an absolute magnitude of 6.9 mag, making it similar to the Milky Way’s ultra-diffuse satellite galaxies. Only an elderly metal-poor star population appears to populate the UFD.
ACCORDING TO THE RESEARCHERS, Tucana B’s brilliance, apparent lack of star formation, and neutral gas make it unique among recent discoveries at this distance.
Furthermore, Tucana B’s extraordinary isolation could indicate that, rather than contact with a bigger galaxy halo, its star development was stifled by reionization or some other internal cause.
Tucana B is a promising target for future space-based follow-up observations aimed at determining its structure and star formation history, maybe down to the oldest main-sequence turnoff, according to Sand’s team.
The researchers stated that “Tucana B may provide a conclusive opportunity to grasp the function that reionization plays in the quenching of the weakest galaxies.”
They went on to say that more objects like Tucana B are needed to better understand the demographics of the UFD population in the field.