JWST sees the beginning of the space web

space web It is the large-scale structure of the universe. If you could observe the evolution of our universe from the Big Bang to the present, you would see that these threads (and the spaces between them) have formed over time. Now using JWST, astronomers have found ten galaxies that form a very ancient version of this structure just 830 million years after the beginning of the universe.

The “cosmic web” began very early in the universe as density fluctuations. A few hundred million years after the Big Bang, matter (in its primordial gaseous form) condensed into knots at the intersection of layers and gas fibers in the early lattice. These knots and threads contained the first stars and galaxies. It is natural for astronomers to look back in time to look for early versions of the cosmic web. JWST allowed them to look back at very faint, dim objects that existed shortly after the Big Bang.

The ten galaxies observed by the team are contained in a thin thread three million light-years long anchored by a bright quasar. Its appearance surprised the team with both its size and its place in space history. “This is one of the oldest filamentous structures that humans have found associated with a distant quasar,” added Feige Wang of the University of Arizona in Tucson, who is the principal investigator of the program.

The quest to understand the early universe and the cosmic web

JWST observations are part of an observation program called ASPIRE: Spectroscopic investigation of biased halos in the Age of Reionization. It uses both images and spectra of 25 quasars that existed when the universe began to glow after the “dark ages.” The idea is to study the formation of the earliest possible galaxies and the birth of the first black holes. Additionally, the team hopes to understand how the early universe was enriched with heavier elements (metals) and how all this happened during the reionization period.

ASPIRE’s goals are an important part of understanding the origin and evolution of the universe. “The past two decades of cosmological research have given us a clear understanding of how the cosmic web formed and evolved. ASPIRE is trying to understand how the emergence of the first massive black holes will be incorporated into our current history of cosmic structure formation,” explained team member from the University of California, Santa Barbara. Joseph Hannawi.

Focus on the first black holes

Quasars call in time and space. They are powered by supermassive black holes, which, along with powerful jets, produce an incredible amount of light and other radiation. Astronomers use them as standard candles to measure distance and as a way to study large regions of space through which light passes.

At least eight quasars in the ASPIRE study have black holes that formed less than a billion years after the Big Bang. The mass of these black holes is between 600 million and 2 billion solar masses. It’s really pretty big, and it raises a lot of questions about their rapid growth. “To create these supermassive black holes in such a short time, two criteria need to be met. First, you need to start growing from a huge “seed” black hole. Second, even if that seed starts with a mass equivalent to a thousand Suns, it will still be possible in its lifetime. At its highest rate it still has to accumulate a million times more matter.”

These black holes needed a lot of fuel to grow. Their galaxies were also quite large, which could explain the terrifying black holes in their hearts. Not only did these black holes absorb a lot of material, but their outflow also affected star formation. “Strong winds from black holes can inhibit star formation in the main galaxy. Such winds have been observed in the near universe, but not directly during the reionization period,” Yang said. “The scale of the wind is related to the structure of the quasar. In Webb’s observations, we see that such winds existed in the early universe.”

Why Epoch?

We often hear that astronomers want to look back at the age of reionization. Why is this such an attractive target? It offers a glimpse into when the first stars and galaxies were formed. After the Big Bang, the baby universe was in a hot and dense state. Sometimes we hear it called the primordial soup of space. Then the expansion started and everything started to cool. This allowed electrons and protons to come together to form the first neutral gas atoms. It also allowed the thermal energy of the Big Bang to spread. Astronomers detect this radiation. This is a redshift towards the microwave portion of the electromagnetic spectrum. Astronomers call this radiation the “cosmic microwave background” (CMB).

This aspect of the early universe had slight fluctuations in the density of the expanding material. This material was neutral hydrogen. There were no stars or galaxies yet. Eventually, however, these denser regions began to clump together under the influence of gravity, causing neutral matter to clump together as well. This caused the high-density regions to collapse further and eventually the first stars to be born. They heated the surrounding material making holes in the neutral areas and this allowed the light to travel. Essentially, these holes (or bubbles) in the neutral gas allowed ionizing radiation to travel further into space. It was the beginning of the age of reionization. One billion years after the Big Bang, the universe was completely ionized.

So how are the first supermassive black holes explained?

Interestingly, the first galaxies discovered by JWST were already completely in place, with supermassive black holes at their cores, along with their quasars. The key question is: How did they grow up so quickly? Their presence could tell astronomers about the “extreme density” in the newborn cosmos. First, a super-dense region full of galaxies is needed to “seed” a black hole.

However, observations prior to the JWST discovery have so far revealed only a few extremely dense galaxies around the oldest supermassive black holes. Astronomers need to make more observations during this period to explain why this might happen. The ASPIRE program will help resolve the feedback problem between the formation of galaxies and the formation of black holes in this very early period of the universe. Along the way, they also need to see more pieces of the universe’s large-scale cosmic web structure as it forms.