The cosmic web is the largest structure in the universe, consisting of filaments of gas, dust, and dark matter that connect galaxies and clusters. However, it is also very faint and hard to observe directly. Until now, astronomers have relied on the bright light of quasars, the most luminous objects in the universe, to illuminate the cosmic web and reveal its structure.
But a team of astronomers from the California Institute of Technology (Caltech) has developed a new technique to image the cosmic web without needing quasar light. They used a special instrument called the Keck Cosmic Web Imager (KCWI), which can detect the faint emission of hydrogen gas, the main component of the cosmic web. By subtracting the background light from various sources, such as the atmosphere, the solar system, and our galaxy, they were able to isolate the signal from the cosmic web and create a three-dimensional map of its filaments.
A Long and Narrow Filament Discovered
The team applied their technique to a region of space between 10 billion and 12 billion light-years away, where they discovered a long and narrow filament of 10 galaxies that spanned 3 million light-years. The filament was anchored by a very distant and luminous quasar, which outshone its host galaxy. The team believes that this filament is one of the earliest strands of the cosmic web, formed just 830 million years after the big bang, and that it will eventually evolve into a massive cluster of galaxies.
The discovery was published in the journal Nature Astronomy and is part of a larger project called ASPIRE (A SPectroscopic survey of biased halos In the Reionization Era), which aims to study the cosmic environments of the earliest black holes. The project will observe 25 quasars that existed within the first billion years after the big bang, a time known as the Epoch of Reionization.
Implications for Cosmology and Galaxy Formation
The cosmic web is a key component of cosmology, as it reflects the distribution of matter and energy in the universe. By mapping its structure and evolution, astronomers can test their models of how the universe formed and grew over time. The cosmic web also plays a crucial role in galaxy formation, as it provides gas for star formation and influences how galaxies interact with each other.
The new technique developed by the Caltech team opens up new possibilities for exploring the cosmic web in more detail and in different regions of space. It also allows astronomers to study how galaxies are affected by their surroundings and how they contribute to shaping the cosmic web.
