Cape Town - An international team of astronomers led by Professor Gyula Józsa, Professor Michelle Cluver and Professor Thomas Jarrett from the Department of Astronomy at UCT have discovered a mysterious chain of hydrogen gas clouds, the size of a massive galaxy.
And this is all thanks to the South African MeerKAT telescope, helping spot the accumulation of so much elemental hydrogen without associated stellar components which is the largest yet discovered.
Appearing at the edge of a relatively massive group of galaxies, there is the possibility that the cloud chain is gas stripped from group-member galaxies, but it may also be primordial and gravitationally drawn into the group through a cosmic filament pathway.
Whatever the case, MeerKAT is proving to be a ground-breaking telescope, and many such discoveries should soon follow this "dark" cloud discovery in the exciting days ahead.
The findings have been published in the Astrophysical Journal.
"It is very puzzling to see such a massive and large gas cloud without a “host” galaxy, or simply, where are the stars? The hydrogen is the fuel for star formation, and so where you have a lot of hydrogen, amassed into a dense object, you have stars (or better, a galaxy of stars). So, it is quite a discovery,” said Jarrett.
“Other ‘dark’ clouds have been seen of course, going back decades, but nothing this large or concentrated like a big galaxy. What I think is that these things exist, perhaps in large numbers, but it required a new and amazing telescope — MeerKAT — to finally see them.”
Jarrett said the project started five years ago, in 2016, with investigation of a particular region of the sky called G23 (GAMA Field 23), in which they have optical redshifts and infrared imaging.
“We have been working on understanding the galaxy distribution and evolution. We then proposed MeerKAT observations (in 2019) to go after a cosmic filament in our field, a very interesting large-scale object in its own right, worthy of additional study,” said Jarrett.
Of the discovery he says: "One day I was looking at the data — the data cube that is — using our new VR system developed by the IDIA/UCT-Astro Visualisation Laboratory, and by golly, I noticed this strange-looking object in the hydrogen gas emission.”
He said the discovery has huge implications because it was found relatively easily, and the team suspects that it must be more common.
“It may be a completely new type of object, and that always leads to a new understanding of nature, or it might be a new class of object, common but not seen until now, that will also lead to new insights with galaxy evolution,” said Jarrett.