Remaining galactic ‘nuggets’ could reveal secrets of the early universe

As more and more recent images from the James Webb Space Telescope continue to arrive, astronomers have spent a lot of time staring at the red dots, trying to understand the composition of galaxies.

As we wait for the dust to settle in the race to find the most redshift systems, to locate the “most distant galaxy ever known,” a team of astronomers led by Krzysztof Lisiecki in Poland have been curious about red systems a little closer to home.

Galaxy Markarian 1216, observed in X-ray light by the Chandra X-ray Observatory, is an oval that may descend from a galaxy

Galaxy Markarian 1216, observed in X-ray light by the Chandra X-ray Observatory, is an elliptical shape that may descend from a “red solid mass” galaxy. Credit: X-ray: NASA/CXC/Univ. From CA Irvine/D. bot

Using data from the VIMOS spectrometer on the Very Large Telescope, they identified a group of nearby “red solid mass” galaxies, the local equivalent of a system class first discovered in the early universe.

The gold nuggets deserve their name, being compact and often massive, red galaxies that reveal a lack of continuous star formation (resulting in a sprinkling of bright blue stars).

Previous work showed that in the early universe, such systems glowed brightly in X-rays, an indication of activity around supermassive black holes that may be responsible for the lack of star formation.

These jewel-like systems are important because they are thought to merge to form the giant elliptical galaxies we see in local clusters such as the Virgo cluster.

A deep image of the Virgo Cluster taken by the Borrell-Schmidt telescope.  Credit: Chris Mihos (Case Western Reserve University) / ESO

A deep image of the Virgo Cluster taken by the Borrell-Schmidt telescope. Credit: Chris Mihos (Case Western Reserve University) / ESO

But studying small, remote, hard-to-resolve systems makes it hard to test this theory.

That’s why the team set out to find the remains of local nuggets that may have survived to the present day.

They started with the 90,000 galaxies that the VLT observed, picking out massive, small, and red galaxies.

This sounds simple, but every decision that is made can change the nature of the final group of galaxies.

For example, the team particularly agonizes over the definition of “agreement.”

We know that the red shards appear to be particularly dense, with lots of stars stacked into a small system, but no one has been able to agree on how that translates into an agreed-upon standard.

middle-aged lonely,

Middle-aged loners, “Red Nuggets” are remnants of the early universe. Credit: X-ray: NASA/CXC/MTA-Eötvös University/N. Werner et al. , illustration: NASA/CXC/M. Weiss

The researchers are conservative, keeping only the most dangerous systems, but this means that the result of all this work was a sample of only 77 new nuggets, with redshifts indicating that their light has been traveling toward us for more than six billion years, roughly half the age of the universe.

Thus these new systems belong to the middle age of the universe, and there are fewer of them at the height of star formation and galaxy clustering four billion years ago.

If these are the components that make up massive elliptical galaxies, then the stars in such systems must have formed long ago.

In the center of this image is an elliptical galaxy, which is the brightest member of the 2261 Abell galaxy cluster. A study shows that galaxies like this wobble could rock our current understanding of dark matter.  Image credit: NASA, European Space Agency, M.  Postman (Space Telescope Science Institute, USA), T. Lauer (National Optical Astronomical Observatory, USA), and the Clash Team.

In the center of this image is an elliptical galaxy, the brightest member of the 2261 Abell galaxy cluster. Credit: NASA, ESA, M. Postman (Space Telescope Science Institute, USA), T. Lauer (National Optical Astronomical Observatory, USA ), and the CLASH team.

The most important clue to the fate of these galaxies is their environment: are they found in massive galaxy clusters, or in the empty spaces between these structures?

The answer to this question will have to wait some time, as the team is still working on it, but the sample they have already collected is unique.

I’m sure they’re not the only ones who will be looking at this new set of red gems scattered across the southern sky.

Chris Lintott was reading First catalog of spectroscopically confirmed red atoms at z ~ 0.7 from the VIPERS survey. Connecting red high z nuggets and local effects By Krzysztof Lisiecki et al. Read it online at: arxiv.org/abs/2208.04601.

This article originally appeared in the October 2022 issue of BBC Sky at Night Magazine.

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