Webb reveals the giant of the early universe

Detailed images of one of the first galaxies show that growth in the early universe was much faster than first thought.

Astronomers are currently enjoying a fruitful period of discovery, investigating many of the mysteries of the early universe.

The successful launch of the James Webb Space Telescope (JWST), the successor to NASA's Hubble Space Telescope, has pushed the limits of what we can see.

Observations now enter the first 500 million years after the Big Bang when the universe was less than five percent of its current age. For humans, this time will firmly put the universe into the toddler stage.

However, the galaxies we observe are certainly not infantile, as new observations reveal galaxies that are more massive and mature than previously expected at such early times, helping to rewrite our understanding of galaxy formation and evolution.

Our international research team recently made unprecedented detailed observations of one of the oldest known galaxies – dubbed Gz9p3, now published in Nature astronomy.

Its name comes from Glass collaboration (name of our international research team) and the fact that the galaxy has a redshift of z=9.3 where redshift is one way of describing the distance to an object – hence G and z9p3.

Gz9p3, the brightest merged galaxy known in the first 500 million years of the universe (observed by the James Webb Space Telescope). Left: Live imaging shows a double nucleus within the central region. Right: Light cross-section features reveal an elongated, clumpy structure resulting from merging galaxies. Credit: NASA

Just two years ago, the Gz9p3 emerged as a single point of light through Hubble Space Telescope. But using James Webb Space Telescope We can observe this object as it was 510 million years later the great explosionabout 13 billion years ago.

We found that Gz9p3 was more massive and mature than expected for such a young universe, and indeed contained several billion stars.

By far, it was the most massive object confirmed since that time, and was calculated to be ten times larger than any other galaxy discovered in the early universe.

Together, these results suggest that for the galaxy to reach this size, stars must have evolved faster and more efficiently than we initially thought.

Merger of the most distant galaxies in the early universe

Not only is Gz9p3 massive, its complex shape immediately identifies it as one of the oldest galaxy mergers ever seen.

The JWST imaging of the galaxy shows a morphology typically associated with two interacting galaxies. The merger is not finished because we still see two components.

When two massive objects come together like this, they get rid of some matter in the process. So, this discarded material suggests that what we've observed is one of the most distant mergers ever.

The James Webb Telescope – the largest and most powerful instrument of its kind ever launched into space – uses a 6.5-meter primary mirror, made of 18 hexagonal mirrors, covered in a layer of gold to produce some of the oldest images of the universe. Image credit: NASA GSFC/CIL/Adriana Manrique Gutierrez

Next, our study delved deeper, to characterize the clusters of stars that make up the merging galaxies. Using JWST, we were able to examine Galaxy spectrumsplits light in the same way that a prism splits white light into a rainbow.

When using imaging alone, most studies of these very distant objects show only very young stars because younger stars are brighter and thus their light dominates the imaging data.

For example, a bright young population created by galactic merger, less than a few million years old, is outpacing an older population that is already more than 100 million years old.

using Spectral analysis technique We can produce such detailed observations, that the two groups can be distinguished.

New models of the early universe

Such a large older population would not have been expected given how early stars formed to be old enough by this cosmic time. The spectroscopy is so detailed, we can see the subtle features of ancient stars that tell us there is more out there than you think.

Specific elements detected in the spectrum (including silicon, carbon, and iron) reveal that this older population must be present to enrich the galaxy with an abundance of chemicals.

It is not only the size of the galaxies that is surprising, but also the speed with which they have grown to this chemically mature state.

These observations provide evidence for a rapid and efficient accretion of stars and metals in the immediate aftermath of the Big Bang, associated with ongoing galaxy mergers, showing that massive galaxies containing many billions of stars existed earlier than expected.

The observations provide evidence of rapid and efficient accretion of stars and metals in the immediate aftermath of the Big Bang. Image credit: NASA, ESA, Jennifer Lutz (STScI), Matt Mountain (STScI), Anton M. Koikimore (STScI), HFF Team (STScI)

Isolated galaxies build their populations of stars On site However, with their limited supply of gas, this can be a slow way for galaxies to grow.

Interactions between galaxies can attract new streams of pure gas, providing the fuel needed for rapid star formation, and mergers provide a more rapid channel for mass accretion and growth.

The largest galaxies in our modern universe have a history of mergers, including our own milky way It has grown to its present size through successive mergers with smaller galaxies.

These observations of Gz9p3 show that galaxies were able to rapidly accumulate mass in the early Universe through mergers, with star formation efficiency higher than we expected.

These and other observations using the James Webb Space Telescope are prompting astrophysicists to revise their models of the universe's early years.

Our cosmology is not necessarily wrong, but our understanding of how quickly galaxies form may be wrong, because they are much larger than we thought possible.

These new findings come at a good time as we approach the two-year mark for scientific observations made with the James Webb Space Telescope.

As the total number of observed galaxies increases, astronomers studying the early universe are moving from the discovery phase to a period when we have samples large enough to begin building and refining new models.

There has never been a more exciting time to understand the secrets of the early universe.

Reference: “A massive interacting galaxy 510 million years after the Big Bang” by Kristan Boyett, Michele Trinti, Nisha Lithokawalit, Antonello Calabro, Benjamin Metha, Guido Roberts Borsani, Niccolò Dalmaso, Lilan Yang, Paola Santini, Tommaso Trio, Tucker Jones. Alaina Henry, Charlotte A. Mason, Takahiro Morishita, Themia Nanayakkara, Namrata Roy, Chen Wang, Adriano Fontana, Emiliano Merlin, Marco Castellano, Diego Paris, Marusha Bradac, Matt Malkan, Danilo Marchesini, Sara Mascia, Karl Glezbrook, Laura Pinterici. , Eros Vanzella and Benedetta Vulcani, March 7, 2024, Nature astronomy.
doi: 10.1038/s41550-024-02218-7

The study was led by Dr Kate Boyett with a team including Professors Michael Trinity and Benjamin Mitha Niccolò Dalmaso Also from the University of Melbourne and ARC Center of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D). An international research team is formed 27 authors from 19 institutions in Australia, Thailand, Italy, USA, Japan, Denmark and China.