New galactic protoamas discovered in the early universe

The newly discovered protocluster, named PHz G237.01 + 42.50 (G237 for short), contains more than 60 members, including galaxies forming blue stars and active galactic nuclei. G237 is so far away that its light has traveled for over 10.6 billion years.

Several instruments have joined forces to produce this image of protoamas G237, identifying its galaxies in different colors representing different wavelengths of observations. The image on the right zooms in on the central region of G237. Image credit: ESA / Herschel / XMM-Newton / NASA / Spitzer / NAOJ / Subaru / Large Binocular Telescope / ESO / VISTA / Polletta et al. / Koyama et al.

“This discovery is an important step towards achieving our ultimate goal: to understand the assemblage of galaxy clusters, the most massive structures that exist in the Universe,” said Dr. Brenda Frye, astronomer at the Observatory. Steward of the University of Arizona.

Originally discovered by ESA’s Planck telescope as part of a whole-sky study, G237 has appeared prominently in the far infrared region of the electromagnetic spectrum.

The sightings looked promising, but to confirm its identity it took follow-up observations with other telescopes.

Dr Frye and his colleagues made observations using the combined power of the Large Binocular Telescope in Arizona and the Subaru Telescope in Japan.

Astronomers have identified a total of 63 galaxies belonging to the G237 protoamas.

“You can think of galaxy protoamas such as G237 as a galaxy shipyard in which massive galaxies are assembled, only this structure existed at a time when the Universe was 3 billion years old,” Dr Frye said.

“At the same time, the genealogy may be closer than you think. Because the Universe is homogeneous and the same in all directions, we believe the Milky Way may have docked to a protocluster node similar to G237 when it was very young.

At first, G237’s observations implied too high a total star-forming rate, and the team struggled to make sense of the data.

Protoamas G237 appeared to be forming stars at a rate 10,000 times greater than that of the Milky Way.

At this rate, the protocluster should quickly use up its star fuel and subsequently settle into a complex system similar to the Virgo supercluster.

“Each of the 63 galaxies so far discovered in G237 has been like an overdrive star factory,” said Dr Frye.

“It’s like the galaxies are working overtime to put the stars together. The rate of production was unbearable. At such a rate, supply chains are expected to break down in the near future, and in a way that will shut down the galaxy shipyard for good. “

Such high yields could only be maintained by continuous injection of fuel, which for the stars is hydrogen gas.

“It would require an efficient, uninterrupted supply chain that sucked unreasonable amounts of fresh gas to power star-forming factories. We don’t know where that gas came from,” Dr Frye said.

Later, the researchers found that part of what he was seeing was from galaxies unrelated to the protoamas, but even after the irrelevant observations were removed, the total rate of star formation remained high, at least. 1,000 solar masses per year. In comparison, our own Milky Way galaxy produces about one solar mass each year.

“The picture we have pieced together now is that of a successful galactic shipyard, which works at high efficiency to assemble the galaxies and stars within them and has a more sustainable energy supply,” Dr Frye said. .

The results were published in the journal Astronomy & Astrophysics.


Mr. Polletta et al. 2021. Spectroscopic observations of PHz G237.01 + 42.50: A galaxy protocluster at z = 2.16 in the Cosmos field. A&A 654, A121; doi: 10.1051 / 0004-6361 / 202140612

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