Direct imaging of a cosmic filament connecting two quasar-host galaxies

In the vast expanse of the universe, galaxies are not isolated islands but are interconnected through a vast network known as the “cosmic web.” This intricate structure, composed of dark matter and gas, forms the backbone of the cosmos, guiding the formation and evolution of galaxies. Recent advancements have allowed astronomers to capture a high-definition image of a filament within this web, providing unprecedented insights into the universe’s large-scale structure.

The Cosmic Web

The cosmic web is a colossal network of filaments stretching across the universe, connecting galaxy clusters and spanning millions of light-years. These filaments are primarily composed of dark matter—a mysterious form of matter that does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects. Alongside dark matter, these filaments contain diffuse gas, predominantly hydrogen, which serves as the raw material for star formation within galaxies.

Theoretical models and simulations have long predicted the existence of this web-like structure. However, directly observing these faint filaments has been a significant challenge due to their diffuse nature and the limitations of previous astronomical instruments.

Breakthrough observations with MUSE

A recent study ¹ has achieved a groundbreaking observation of a cosmic filament. Utilizing the Multi-Unit Spectroscopic Explorer (MUSE) instrument mounted on the Very Large Telescope (VLT) in Chile, the team captured a high-definition image of a filament connecting two quasar-host galaxies at a redshift of approximately 3.22, corresponding to a time when the universe was about 2 billion years old.

Quasars are extremely luminous active galactic nuclei powered by supermassive black holes accreting matter. The intense radiation from quasars can illuminate the surrounding intergalactic medium, making it possible to detect the otherwise faint emission from cosmic filaments. In this study, the proximity of two quasars provided an ideal laboratory for observing the connecting filament in unprecedented detail.

The observations revealed a filament extending over 3 million light-years, connecting the two quasar-host galaxies. This detection allowed researchers to:

1. Characterize Filament Morphology: The high-definition imaging provided a detailed view of the filament’s structure, confirming theoretical predictions about the shape and distribution of matter within cosmic filaments.
2. Measure Transition Radius: The study identified the boundary between the circumgalactic medium (the gas enveloping individual galaxies) and the intergalactic medium within the filament. This measurement is crucial for understanding how galaxies acquire gas to fuel star formation.
3. Surface Brightness Profiles: By analyzing the brightness of the filament along its length and across its width, the team gained insights into the density and temperature of the gas within the filament.

These findings are consistent with the current cold dark matter model of the universe, validating predictions about the density and distribution of matter in cosmic filaments.

A pivotal moment in observational cosmology

This study represents a significant advancement in our ability to observe and understand the cosmic web. Directly imaging these filaments provides critical data to test cosmological models as observations of the cosmic web serve as a benchmark for cosmological simulations, allowing scientists to refine models of the universe’s evolution and the role of dark matter. Furthermore, the cosmic web plays a fundamental role in channeling gas into galaxies, influencing star formation rates and the growth of galaxies over cosmic time. By studying these filaments, researchers can better understand the processes that govern galaxy formation and evolution.

The success of this study opens new avenues for exploring the cosmic web. With advancements in telescope technology and instrumentation, astronomers anticipate mapping larger regions as future surveys aim to map extensive portions of the cosmic web, providing a more comprehensive view of the large-scale structure of the universe; investigating the physical conditions that govern star formation and galaxy growth; and, since dark matter constitutes a significant portion of the cosmic web, studying these structures can offer indirect insights into the nature of dark matter, one of the most profound mysteries in modern astrophysics.

The direct imaging of a cosmic filament connecting two quasar-host galaxies marks a pivotal moment in observational cosmology. It not only confirms longstanding theoretical predictions but also enhances our understanding of the universe’s large-scale structure and the intricate processes that drive galaxy formation and evolution. As observational techniques continue to improve, we stand on the brink of uncovering even more secrets of the cosmic web, bringing us closer to comprehending the vast and complex universe we inhabit.

Author: César Tomé López is a science writer and the editor of Mapping Ignorance

Disclaimer: Parts of this article may have been copied verbatim or almost verbatim from the referenced research paper/s.