Astronomy: A dense cluster of galaxies

The discovery of a massive and extremely dense protocluster - the progenitor of a galaxy cluster - is reported in Nature this week.

During a survey of a region of the sky, the South Pole Telescope discovered a population of rare, extremely bright sources. Using sensitive observations of carbon monoxide and ionized carbon emissions, Tim Miller and colleagues report that the brightest of these sources, called SPT2349-56, consists of a protocluster of at least 14 gas-rich galaxies that are rapidly forming stars. The authors also report that the galaxies are located within a concentrated region of only approximately 130 kiloparsecs in diameter.

Measurements of both the continuum and spectral lines of the 14 galaxies allowed the authors to estimate their star formation properties, and they conclude that each galaxy is forming stars between 50 and 1,000 times faster than the Milky Way.

A comparison with other known protoclusters at high redshifts suggests that SPT2349-56 is a uniquely massive and dense system that could be building one of the most massive structures in the Universe today. The authors suggest that this system represents a galaxy cluster core that was at an advanced stage of formation when the Universe was only 1.4 billion years old.

doi: 10.1038/s41586-018-0025-2

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