20,000 galaxies in a single image: the new James Webb's new wonder

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Understanding the history of the universe is possible thanks to space and ground-based telescopes and observatories. When we point our instruments at distant objects we receive light emitted hundreds, thousands, millions or even billions of years ago. Projects like EIGER seek to take advantage of James Webb's high resolution to study the evolution of galaxies in the early universe.

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Full false-color field of the new James Webb image with more than 20,000 galaxies visible. The observation is centered on the quasar J0100+2802, which shows a pink hue and six diffraction peaks. Credits: NASA, ESA, CSA, S. Lilly (ETH Zurich), D. Kashino (Nagoya University), J. Matthee (ETH Zurich), C. Eilers (MIT), R. Simcoe (MIT), R. Bordoloi (MIT), R. Mackenzie (ETH Zurich), A. Pagan (STScI).

The era of reionization

Current models place the origin of the universe in the so-called Big Bang, the instant at which an infinitesimal point expanded vertiginously to give way to everything we know today. In the beginning there was a high energy density and particles could not join together; for example, protons and electrons to form atoms. Along with the growth of space, temperatures dropped and finally the first elements appeared.

Over time the atoms reached stable and electrically neutral configurations, allowing the flow of light in what is known as the transparent universe.. However, the formation of the first stars and galaxies led to the appearance of intense X-ray and gamma-ray sources. They have the ability to ionize or remove electrons from the elements.

Understanding the ionization processes and ratios of the gas gives us the key tool to estimate star formation rates as well as their final distribution. The EIGER projectThe term "emission lines in galaxies and intergalactic gas in the era of reionization" stands for emission lines in galaxies and intergalactic gas in the era of reionization, will use seven quasar-centered observations to model ionization in the vicinity of very high-energy sources.            

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Close-up of six full-field galaxies captured by the NIRCam instrument. They feature irregular, elongated shapes and reddish and pinkish hues with small blue and purple markings. Credits: NASA, ESA, CSA, S. Lilly (ETH Zurich), D. Kashino (Nagoya University), J. Matthee (ETH Zurich), C. Eilers (MIT), R. Simcoe (MIT), R. Bordoloi (MIT), R. Mackenzie (ETH Zurich), A. Pagan (STScI)

Quasar J0100+2802

The first of the observations was focused on the object called J0100+2802, a galaxy whose great brightness is due to a supermassive black hole whose light resembles that of a lighthouse. The study focused on 117 of the 20 000 galaxies visible in the full field, which existed when the universe was about 900 million years old, i.e, before the era of reionization.

The galaxies present at that time provided sufficient energy to create small transparent gas bubbles. Their sizes resemble the separation between the Milky Way and Andromeda, as well as a hot air balloon that was expanding and merging exponentially until it covered the entire universe.

Due to the great distances that light must travel and the expansion of the universe, it undergoes a process known as redshift, where the wavelength is stretched until it reaches the infrared zone. Thus giving the characteristic reddish hue of the youngest galaxies. These galaxies show irregular and elongated shapes, with a considerable rate of formation of massive stars that will give way to fantastic supernovae.

Exploring the past

EIGER is just one of many initiatives that use James Webb data to contribute to the understanding of everything around us and its respective origin. Although the original plan was to study seven targets, the first data provided by the NIRCam instrument are of sufficient quality to make important discoveries.

Francisco Andrés Forero Daza