Digital illustration of cosmic infrared background lensing by dark matter.

Unlocking the Universe's Secrets: How Cosmic Infrared Background Helps Map Dark Matter

Lena Voss in Science & Nature June 2025 • 4 min read.

"Delving into the innovative use of cosmic infrared background (CIB) to illuminate the universe's hidden structures."

Imagine the universe as a vast, intricate tapestry woven with stars, galaxies, and unseen structures. For decades, scientists have been developing methods to map the distribution of matter, including the elusive dark matter that makes up a significant portion of the cosmos. Gravitational lensing, the bending of light by massive objects, has emerged as a powerful tool in this endeavor. By observing how light from distant sources is distorted, researchers can infer the presence and distribution of intervening mass, offering insights into the universe's underlying framework.

Traditionally, gravitational lensing studies have focused on two primary sources: the cosmic microwave background (CMB) and individual galaxies. The CMB, the afterglow of the Big Bang, provides a pristine canvas for mapping the large-scale structure of the universe. Galaxy surveys, on the other hand, allow scientists to probe the distribution of matter on smaller scales by analyzing the shapes and orientations of distant galaxies. Now, a new player has entered the field: the cosmic infrared background (CIB).

The CIB, a diffuse glow of infrared light emitted by countless dusty star-forming galaxies, offers a unique perspective on the universe's structure. Unlike the CMB, which originates from a single epoch in cosmic history, the CIB is sourced by galaxies spanning a wide range of redshifts, or distances. This makes it an ideal probe of the universe's structure at intermediate redshifts, bridging the gap between galaxy surveys and CMB lensing studies.

CIB Lensing: A New Window on the Cosmos

Digital illustration of cosmic infrared background lensing by dark matter.

Recent research has demonstrated the potential of using the CIB as a source for gravitational lensing studies. By analyzing the distortions in CIB maps, scientists can reconstruct the distribution of matter along the line of sight, providing valuable information on the amplitude of structure at intermediate redshifts. This approach complements existing lensing techniques and offers new insights into the formation and evolution of galaxies and the overall structure of the universe.

One of the key advantages of CIB lensing is its sensitivity to the distribution of matter at redshifts between those typically probed by galaxy surveys and the CMB. This allows scientists to track the growth of structure across cosmic time and test cosmological models. Additionally, CIB lensing measurements can provide valuable information on the star-formation history of the universe, constraining models of galaxy evolution and the properties of the halos in which galaxies reside.

Bridging the Gap: CIB lensing probes intermediate redshifts between galaxy surveys and CMB lensing.
Star-Formation History: Constrains CIB halo models and informs about the universe's star-formation.
Structure Amplitude: Provides constraints on the amplitude of structure at different cosmic times.

However, CIB lensing also presents unique challenges. Unlike the CMB, which is nearly Gaussian, the CIB exhibits non-Gaussianity due to the clustering of galaxies. This non-Gaussianity can introduce biases and complicate the analysis of CIB maps. Researchers are actively developing methods to mitigate these effects, including advanced statistical techniques and careful modeling of the CIB emission.

The Future of CIB Lensing

As data from current and future experiments become available, CIB lensing promises to become an increasingly powerful tool for unraveling the mysteries of the universe. By combining CIB lensing with other cosmological probes, scientists will be able to create a more complete and accurate picture of the universe's structure, evolution, and composition. The journey into the depths of the cosmos continues, guided by the faint but informative glow of the cosmic infrared background.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1103/physrevd.97.123539, Alternate LINK

Title: Weak Lensing Of Intensity Mapping: The Cosmic Infrared Background

Journal: Physical Review D

Publisher: American Physical Society (APS)

Authors: Emmanuel Schaan, Simone Ferraro, David N. Spergel

Published: 2018-06-27

Everything You Need To Know

How does gravitational lensing help scientists map dark matter and the universe's structure?

Gravitational lensing uses the bending of light by massive objects to map the distribution of matter in the universe. By observing how light from distant sources is distorted, scientists can infer the presence and distribution of intervening mass, including dark matter. This technique provides insights into the universe's underlying structure. Traditional methods use the cosmic microwave background (CMB) and individual galaxies as primary light sources for this analysis.

What makes the cosmic infrared background (CIB) a unique source for gravitational lensing compared to the cosmic microwave background (CMB)?

The cosmic infrared background (CIB) offers a unique advantage by probing the universe's structure at intermediate redshifts, which bridges the gap between galaxy surveys and CMB lensing studies. Unlike the CMB, which originates from a single epoch, the CIB is sourced by galaxies spanning a wide range of distances, making it ideal for studying the universe's structure over a broad range of cosmic times. This is crucial for understanding how structures like galaxies and galaxy clusters have evolved.

In what ways does CIB lensing contribute to our understanding of the universe's structure and galaxy evolution?

CIB lensing allows scientists to track the growth of structure across cosmic time and test cosmological models. By analyzing distortions in CIB maps, researchers can reconstruct the distribution of matter along the line of sight, providing valuable information on the amplitude of structure at intermediate redshifts. Additionally, CIB lensing measurements can provide insights into the star-formation history of the universe, constraining models of galaxy evolution and the properties of the halos in which galaxies reside.

What is non-Gaussianity in the CIB, and why does it pose a challenge for CIB lensing studies?

Non-Gaussianity in the CIB arises from the clustering of galaxies, which can introduce biases and complicate the analysis of CIB maps. This differs from the cosmic microwave background (CMB), which is nearly Gaussian. Researchers are actively developing methods to mitigate these effects, including advanced statistical techniques and careful modeling of the CIB emission. Addressing the non-Gaussianity is crucial for obtaining accurate results from CIB lensing studies.

How will CIB lensing be used in the future to further our understanding of the universe, and what is the importance of combining it with other cosmological probes?

Combining CIB lensing with other cosmological probes will create a more complete and accurate picture of the universe's structure, evolution, and composition. As data from current and future experiments becomes available, CIB lensing promises to become an increasingly powerful tool for unraveling the mysteries of the universe. The future of cosmology involves integrating multiple sources of information to gain a deeper understanding of the cosmos, and CIB lensing is poised to play a significant role in this endeavor.