Once again, galaxies look surprisingly mature shortly after the beginning of the universe

A young galaxy with the catchy name A1689-zD1 has experts in galactic formation talking. Recent observations show that this galaxy, as it would have looked just 700 million years after the Big Bang, is larger than originally thought, with a significant outflow of hot gas from the core and a halo of cold gas emanating from the outer rim. coming. A1689-zD1 is considered representative of young “normal” galaxies (as opposed to “massive” galaxies), and the new observations suggest that normal galaxies’ adolescence may be more turbulent than previous models suggest.

A1689-zD1 was first observed in 2007 by the Hubble Space Telescope and at the time was a contender for the farthest galaxy discovered to date (a record surpassed several times, most recently in April 2022† In fact, it’s so far away that the only reason it’s possible to get such a good view of it is that it’s conveniently located behind a much closer galaxy, whose gravitational interaction with spacetime creates a lens effect, allowing the distant A1689- is enlarged. zQ1 behind. The Spitzer Space Telescope was able to observe the galaxy next to Hubble, but the clearest images of the galaxy were obtained within the Atacama Large Millimeter/submillimeter Array (ALMA), which specializes in wavelengths invisible to the naked eye and well suited to distant objects.

The ALMA data tells a story buried in details that Hubble and Spitzer couldn’t see.

“The emission of the carbon gas in A1689-zD1 is much more extensive than what was observed with the Hubble Space Telescope,” said Seiji Fujimoto, a postdoctoral researcher at the Niels Bohr Institute, “and this could mean that early galaxies are not that small.” as they appear If early galaxies are actually larger than we previously thought, it would have a major impact on the theory of galaxy formation and evolution in the early universe.

The ALMA Observatory, located in Chile’s Atacama Desert. Credit: ESO/C. Pontoni (Wikimedia Commons)

In addition to the surprising size of the A1689-zD1, it also appears to be undergoing a surprisingly high level of star formation in a halo of carbon gas that surrounds the galaxy, although this gas could also be a sign of a galactic merger that took place during the early stages of the galaxy. the formation of a galaxy. Either way, it suggests an unexpectedly dynamic early phase of galaxy formation.

Closer to the galaxy’s core, the team also saw signs of hot, ionized gas that typically represent extreme, energetic events, such as supernova explosions or powerful jets from a black hole’s accretion disk. This hot gas outflow may be related to the cold gas halo further away, and has intrigued the researchers. At least they didn’t expect it in such a young galaxy. “We’ve seen this kind of extended gas halo emission from galaxies that formed later in the Universe, but seeing it in such an early galaxy means that this kind of behavior is universal, even in the more modest galaxies that most have formed stars in the universe.” early universe,” said Darach Watson, associate professor at the Niels Bohr Institute. “Understanding how these processes took place in such a young galaxy is critical to understanding how star formation takes place in the early Universe.”

A1689-zD1, a star-forming galaxy in the constellation Virgo, as seen by ALMA. Gravity lenses make the young galaxy appear nine times brighter. Credit: ALMA (ESO/NAOJ/NRAO)/H. Akins (Grinnell College), B. Saxton (NRAO/AUI/NSF).

Of course, this one observation probably won’t rewrite the textbooks just yet. Researchers will continue to observe the early Universe for galaxies of similar age to determine whether A1689-zD1 is typical in its size and activity, or whether it is an outlier.

The James Webb Space Telescope, which, like ALMA, is well-suited for observing young galaxies at this distance, should soon yield a larger sample to study. he comes online later this summer — though it will also rely on a casual gravitational lens to find and study the earliest galaxies.

You can view the full press release hereand read the preprint ArXiv

Featured Image: Artist’s concept of A1689-zD1. Far beyond the center of the galaxy, shown here in pink, is an abundant halo of cold carbon gas. For scientists, this unusual feature indicates that the galaxy may be much larger than previously believed and that early stages of normal galaxy formation may be more active and dynamic than theorized. At the top left and bottom right, we see outflows of hot, ionized gas pushing out from the center of the galaxy, shown here in red. Scientists believe it is possible that these outflows have something to do with the presence of cold carbon gas in the outer reaches of the galaxy. Credits: ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF)

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