On December 25, 2021, after many years of waiting, James Webb Space Telescope (JWST) finally into space. In the ensuing sixth month, this next-generation observatory fired its sunscreen, deployed its primary and secondary mirrors, aligned its mirror portions, and headed to its current location at Earth-Sun Lagrange 2 (L2) Point. On July 12, 2022, the first images were released and the most detailed scenes of the universe were shown. Shortly thereafter, NASA released an image of the most distant galaxy ever observed (which existed only 300 million years after the Big Bang).
According to a new study by an international team of scientists, JWST will allow astronomers to obtain accurate mass measurements of early galaxies. Using data from the James Webb Near Infrared Camera (NIRCam), which was provided by the GLASS-JWST-Early Release Science (GLASS-ERT) program, the team obtained mass estimates from some distant galaxies that were many times more accurate than previous measurements. Their findings illustrate how Webb will revolutionize our understanding of how the oldest galaxies in the universe grow and evolve.
The research team (led by Paola Santini of the Astronomical Observatory of Rome) included members from the National Institute of Astrophysics (INAF) in Italy, the ASTRO 3D collaboration (Australia), the National Institute for Astronomical Research of Thailand (ARIT), and the Kavli Institute for Astrophysics and Cosmology (KIPAC). ), the Center for Cosmic Dawn (DAWN), the Niels Bohr Institute, the Carnegie Institution for Science, the Center for Infrared Processing and Analysis at the California Institute of Technology, and universities and institutes in the United States, Europe, Australia, and Asia.
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As they point out in their study, stellar mass is one of the most important (if not so) physical properties The Most) to understand the formation and evolution of galaxies. It measures the total number of stars in the galaxy, which are constantly being added by turning gas and dust into new stars. Therefore, it is the most direct means of tracking galaxy growth. By comparing observations of the oldest galaxies in the universe (those that are more than 13 billion light-years away), astronomers can study how galaxies evolved.
Unfortunately, obtaining accurate measurements of these early galaxies has been an ongoing problem for astronomers. Astronomers typically make M/L measurements — where the light from a galaxy is used to estimate the total mass of the stars within — rather than calculating stellar masses on one source after another. Base. So far, studies have been conducted by Hubble Of the more distant galaxies – such as GN-z11, which formed about 13.5 billion years ago – they are restricted to the ultraviolet (UV) spectrum.
This is because light from these ancient galaxies experiences a significant redshift by the time it reaches us. This means that as light travels through spacetime, its wavelength is lengthened due to the expansion of the universe, effectively shifting it toward the red end of the spectrum. For galaxies with a redshift (z) of seven or higher – at a distance of 13.46 light-years or more – much of the light will shift to the point where it is only visible in the infrared part of the spectrum. As Santini explained to Universe Today via email:
“The bulk of stars in galaxies, those that contribute mostly to their stellar mass, emit in infrared (NIR) wavelengths… [B]The time it takes light to travel from a distant galaxy to our telescopes, the light emitted by its stars is no longer present in the optical system. For example, for the az = 7 galaxy, the light originally emitted at 0.6 microns, reaches our telescope with a wavelength of 4.8 microns. The greater the redshift (that is, the farther away the galaxy), the stronger this effect.”
“This means that we need infrared detectors to measure the stellar masses of galaxies (the light emitted by the bulk of their stars is out of reach) Hubble Space Telescope). The only infrared telescope we had before the advent of the JWST telescope was the Spitzer Space Telescope, which was rejected a few years ago. However, its 85cm mirror is not comparable to JWST’s 6.5m mirror. Most of the distant galaxies were out of Spitzer’s reach, too: due to their limited sensitivity and angular resolution, they were not detected (or affected by high levels of noise) in their images.
Moreover, previous surveys would have likely missed a significant portion of the galaxies that are intrinsically red, rich in dust (which block light) and faint in the ultraviolet spectrum. Thus, previous estimates of the stellar mass density of cosmic stars of the early universe could exceed six times. But thanks to its sophisticated suite of infrared instruments and unparalleled sensitivity, JWST is poised to open a “new window” (as Santini said) for studying the oldest and faintest galaxies in the universe. As expressed by Santini, Webb will enable the first-ever accurate measurements of the masses of galaxies to the farthest distances:
“Because of all these limitations in measuring stellar mass, a commonly used technique prior to the launch of JWST was to transform UV light (which can be easily measured by HST) in estimating stellar mass assuming an average ratio of mass to UV radiation. The relationship between mass and light was calibrated using the few and uncertain measurements we had, and were representative only of those galaxies most easily observable (young, dust-free galaxies). Therefore measurements of stellar mass were subject to significant uncertainties (both when measured directly, and even more when inferred from UV light). “
For their study, Santini and his international team of researchers relied on images taken by NIRCam from June 28 to 29, 2022, as part of the first set of its observations. They then measured the stellar masses of 21 distant galaxies (which ranged in redshift from 6.7 to 12.3) by checking the emission of ultraviolet and red optical light. As Santini pointed out, this allowed them to avoid the large extrapolations and uncertainties of previous surveys and to increase the accuracy of mass measurements by a factor of 5 to 10.
“Comparing the stellar masses with UV light (measured by the bluer NIRCam bands), we found that the M/L ratio is far from approximated by one average value,” he said. “It instead extends to nearly two orders of magnitude relative to a given luminosity. From a physical point of view, this result indicates that early galaxy clusters were highly heterogeneous, with galaxies exhibiting a variety of physical conditions.”
These findings are part of a growing body of scientific studies emerging from James Webb’s first observations, and which show just how central the mission is. In this case, being able to provide more restricted estimates of stellar mass in galaxies would greatly help astronomers involved in studying the universe on larger and longer scales (also known as cosmology). Said Santini:
“The main implication is that previous findings related to the process of mass growth in galaxies can be affected by important regular systems. In our work we assess, for example, the level of regular uncertainty affecting cosmic stellar mass density. The latter describes the global growth of galaxies in the universe as a function of time. evaluated in the early ages is subject to considerable variation from one work to another.We find that the systematic uncertainty resulting from the assumption of a standard mass of light can be as high as a small factor, and certainly very large compared to the level of accuracy we aim to reach, and can explain at least in part the mismatch Results of the literature”.
So far, Webb has demonstrated his optical capabilities by taking the clearest and most detailed images of the universe, which are already leading to new discoveries. Its spectrometers have obtained spectra from a distant exoplanet, showing how they will help characterize the atmospheres of exoplanets and determine if they are truly “habitable.” This latest study shows that it will also play a vital role in defining the properties of the first galaxies in the universe, how they have evolved since, and the possible role of dark matter and dark energy.
In-depth reading: arXiv