Astronomers using the NASA/ESA Hubble Space Telescope have detected and studied numerous young star clusters in six merging galaxy systems.
Adamo et al. investigated the rate of star formation within six merging galaxy systems (from left to right, from top to bottom): NGC 3256, NGC 1614, NGC 4194, NGC 3690, NGC 6052, and NGC 34. Image credit: NASA / ESA / Hubble Heritage Team / STScI / AURA / A. Evans / University of Virginia, Charlottesville / NRAO / Stony Brook University / Adamo et al.
“Merging galaxy systems are excellent laboratories to trace cluster formation under extreme gas physical conditions, rare in the local Universe, but typical for star-forming galaxies at cosmic noon,” said Stockholm University astronomer Angela Adamo and her colleagues.
“It is during rare merging events that galaxies undergo dramatic changes in their appearance and in their stellar content.”
“Even after the collision, when the resulting galactic system begins to fade into a more quiescent phase, these very massive star clusters will shine throughout their host galaxy, as long-lasting witnesses of past merging events.”
“The Milky Way typically forms star clusters with masses that are 10,000 times the mass of our Sun,” they noted.
“This doesn’t compare to the masses of the star clusters forming in colliding galaxies, which can reach millions of times the mass of our Sun.”
As part of the Hubble imaging Probe of Extreme Environments and Clusters (HiPEEC) survey, the astronomers searched for young stellar clusters in six merging systems: NGC 34, NGC 1614, NGC 3256, NGC 3690, NGC 4194, and NGC 6052.
They were able to detect numerous clusters with ages between 1 and 500 million years and masses over 10 million solar masses.
To analyze the star formation rate within these systems, the researchers derived star cluster ages, masses, and extinctions.
They found that the star cluster populations undergo large and rapid variations in their properties, with the most massive clusters formed towards the end of the merger phase.
“The recent cluster formation history and their distribution within the host galaxies suggest that systems such as NGC 34, NGC 1614, and NGC 4194 are close to their final coalescing phase, while NGC 3256, NGC 3690, and NGC 6052 are at an earlier/intermediate stage,” they said.
The results were published in the Monthly Notices of the Royal Astronomical Society.
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A. Adamo et al. 2020. Star cluster formation in the most extreme environments: insights from the HiPEEC survey. MNRAS 499 (3): 3267-3294; doi: 10.1093/mnras/staa2380
