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By analyzing the data from the MeerKAT International Giga-Hertz Tiered Extragalactic Exploration (MIGHTEE-HI) survey, astronomers have discovered a new rotating galaxy filament. The newfound filament is about 5.5 million light years long and connects 14 galaxies. The was reported August 18 on the pre-print server arXiv.

Galaxy filaments are the largest known structures in the universe containing galaxies with mixed stellar population types and structures. They inject gas into galaxies, helping them grow and evolve.

Large filamentary structures have only recently been discovered by observations of neutral atomic hydrogen (HI). Studies of the cold HI gas within galaxy filaments can help us better understand the relationship between the low-density gas in the cosmic web and how the galaxies that lie within it grow using this material.

Now, a team of astronomers led by Madalina N. Tudorache of the University of Cambridge, UK, reports the detection of a string of HI galaxies from the MIGHTEE-HI survey.

"In this work, we present the detection of 14 HI galaxies in the MIGHTEE-HI survey at z = 0.03 in the COSMOS field, which form a filamentary-like structure," the researchers wrote in the paper.

All the 14 galaxies lie within a very small range in recessional velocity between 9,230–9700 km/s (with a velocity dispersion of about 140 km/s). They form a linear structure at around 30 degrees west of north on the celestial sphere, with a length of approximately 5.5 million light years and a width of about 117,000 light years.

Moreover, the observations suggest that this galaxy filament is embedded in a much larger cosmic web structure, with a size of at least 49 million light years. This cosmic web filament appears to have a thickness between 2.6 and 3.3 million light years.

The observations found that the reported 14 HI galaxies are significantly more strongly aligned with the cosmic web filament. Therefore, this indicates that the angular momentum of galaxies is closely connected to the large-scale filamentary structure.

Furthermore, by analyzing the collected data, the astronomers found strong evidence for the rotation of the galaxies around the spine of the filament. This finding makes the newly detected galaxy filament the longest and one of the largest spinning structures so far identified.

The obtained results also allowed Tudorache's team to get more insights into the evolutionary stage of the galaxy filament.

"The abundance of HI galaxies along the filament and the low dynamical temperature of the galaxies within the filament indicates that this filament is at an early evolutionary stage where the imprint of cosmic matter flow on galaxies has been preserved over cosmic time," the astronomers conclude.