A week later, astronomers found a galaxy even deeper in time

A week later, astronomers found a galaxy even deeper in time
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The James Webb Space Telescope continues to deliver on its promises in discovering early galaxies.
expand / The James Webb Space Telescope continues to deliver on its promises in discovering early galaxies.


Data from the Webb Space Telescope has only come into the hands of astronomers in the last few weeks, but they’ve been waiting for it for years and their analysis will apparently continue. The result has been something like a race through time, as new discoveries find objects closer than ever to the Big Bang that made up our Universe. Last week, one of these calls A galaxy that existed less than 400 million years after the Big Bang emerged. This week, a new analysis named a galaxy as it appeared just 233 million years after the Universe emerged.

The discovery is a happy by-product of work designed to answer a more general question: How many galaxies should we expect to see at different time points after the Big Bang?

back in time

As we mentioned last week, the early Universe was opaque to light at any wavelength, carrying more energy than is needed to ionize hydrogen. This energy is in the UV part of the spectrum, but the redshift caused by an expanding Universe of 13 billion years has shifted this cutoff point to the infrared part of the spectrum. To find galaxies from this time, we need to look for objects that are invisible at shorter infrared wavelengths (meaning that light was once above the hydrogen limit), but visible at lower energy wavelengths.

The deeper the boundary between the invisible and the visible in the infrared, the stronger the redshift and the farther the object is. The further away the object is, the closer in time it is to the Big Bang.

Studies of these galaxies can tell us something about their individual characteristics. However, identifying a large collection of early galaxies can help us determine how quickly they formed and identify changes in galaxy dynamics at a given time in the Universe’s history. This variation in the frequency of visible objects over time is called the “luminance function,” and some work has been done to characterize the luminosity function of early galaxies. But the infrared wavelengths of the oldest galaxies are absorbed by Earth’s atmosphere and therefore must be viewed from space. And that was one of the design goals of the Webb Telescope.

The new work focused on studying the luminosity function of galaxies that formed (in astronomical terms) shortly after the Big Bang. However, researchers creating a catalog of early galaxies have spotted what appears to be the oldest galaxy ever viewed.

defining the function

The researchers used two data sources to reconstruct the appearances of galaxies at different points in time. One was generated by analyzing work with a ground-based infrared telescope (ESAs). VISTA telescope) and the Spitzer space telescope imaged galaxies that were relatively older when they both produced the light that now reaches Earth—about 600 million years or more after the Big Bang. Other relevant data generated by Webb, including the datasets analyzed in the paper we reported and a displayed area first public photo release. In any case, the researchers looked for the same thing: objects that were found at longer infrared wavelengths but not at shorter ones.

Overall, the team detected 55 distant galaxies, 44 of which had never been noted before. Thirty-nine of these come from Webb data, which includes the two ancient galaxies identified last week. The numbers are not particularly accurate at higher redshifts, where they are based on only one or two galaxies. But overall, the trend shows a gradual decline in visible objects from a few hundred million years after the Big Bang, without sharp changes or interruptions.

But what is striking is that there is data for a galaxy at an extremely large redshift (z = 16.7 for those who understand these things). This places it less than 250 million years after the Big Bang. This distance is based, in part, on the fact that the first wavelength filter the object appeared in showed that it was very dim there, suggesting that it was faint at the wavelengths the filter passed through. This indicates that the light cutoff produced by the hydrogen is near the edge of the filter’s aperture.

Like the distant galaxies announced last week, it also appears to have the equivalent of a billion Suns in the form of stars. Researchers speculate that it may have started star formation as early as 120 million years after the Big Bang, and certainly 220 million years ago.

The researchers are quite confident that this new galaxy represents a real finding: “We’ve searched extensively, and currently we can’t find a plausible explanation for this object other than a galaxy in a new redshift record.” And by adding a second independent verification of previous galaxy findings, it greatly increases our confidence in these discoveries. All this indicates that the new telescope delivered as promised, at least in terms of early galaxies.

The big question now is what will come of when objects are pointed at areas of high lensing that can magnify them to a point where we can view structures in these early galaxies. We may have already done this, but we will have to wait for the annotations to appear in arXiv.

arXiv. Summary number: 2207.12356 (about arXiv).

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