The origin of the universe is cloaked in cosmic dust. This vast expanse is teeming with tiny particles, ranging from a handful of molecules to micrometers – a scale of up to a millionth of a meter, or a hundred thousandth of an inch. From the dawn of the universe to the present day, massive clouds of gas and dust have accumulated and collapsed, giving birth to stars and galaxies. By investigating these particles, scientists can unlock secrets about the early universe. However, dust often obscures many interstellar objects from telescopes, limiting our understanding of deep space.

Astronomers are especially intrigued by a class of distant cosmic entities known as dust-enshrouded star-forming galaxies (DSFGs), which are prolific in star production. These ancient galaxies create over 100 stars annually—nearly ten times the rate of the Milky Way—but their visible light is entirely masked by dust. To decipher high-resolution data, astronomers employ a method known as astronomy to unearth the characteristics of these DSFGs. It’s akin to examining a high-definition 4K image, yet from the far reaches of outer space. Until recently, no equipment could successfully resolve DSFGs. This changed with the advent of the James Webb Space Telescope (JWST).

An international team of astronomers has recently succeeded in resolving 22 DSFGs using the JWST’s near-infrared camera, NIRCam. This advanced instrument can observe galaxies at wavelengths between 0.6 to 5 micrometers (approximately 1/5 millionth of a meter, or 2/1000ths of an inch). Astronomers leverage these high-resolution observations to navigate the dust enveloping DSFGs.

The research team utilized seven distinct filters in NIRCam to isolate specific wavelengths or colors of light from each galaxy. Each filter reveals different physical properties, including the galaxies’ size, shape, lumpiness, mass, and star formation rates. No single filter can capture all properties simultaneously; astronomers must also adjust their filters in accordance with the distance between the galaxy and Earth. Due to the universe’s expansion, older, more distant galaxies like the DSFG are receding from our own, causing the light waves we capture to stretch—a phenomenon known as redshift.

With the high-resolution data, the team classified DSFGs into three categories based on their visual traits. Type I galaxies create stars across their entirety, Type II galaxies concentrate star formation in their cores, while Type III galaxies generate stars only in their outer regions, known as the galactic disk. Astronomers studying cosmic history focus on areas where stars are not forming due to rapid cooling, identifying Type II and Type III galaxies. The study found 10 Type I galaxies, five Type II galaxies, and seven Type III galaxies among the DSFGs analyzed.

The team further explored the internal characteristics of each galaxy to unravel general trends within each type. To gauge their mass and star formation rates, astronomers employed models based on patterns of light emitted by the DSFGs, discovering that their sizes range from 30 billion to 300 billion times that of the Sun. Notably, the most massive DSFGs are smaller than the Milky Way and generate between 25 and 500 stars annually, located between 10 billion and 18 billion light-years from Earth.

The researchers also analyzed the shapes of these galaxies, noting that the more distant and older a galaxy is, the more fragmented its form appears. This fragmentation suggests that the high-redshift DSFGs are in a phase of forming tightly packed collections of stars, a structure known as a bulge. These galaxies may eventually experience quenching at their centers, morphing into Type III galaxies. Furthermore, scientists uncovered a previously unnoticed feature across many galaxies: they exhibit polarization, indicating potential past mergers with other galaxies.

The research team concluded that the high-resolution data provided by JWST can unveil hidden features within DSFGs, aiding astronomers in piecing together their past and predicting future developments. They advocate for upcoming researchers to utilize JWST data to test hypotheses regarding the evolution and characteristics of these fascinating galaxies.

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