Launching for the first time on July 12, 2022, the James Webb Space Telescope Early Release Science (ERS) program has proven to be a treasure trove of scientific discoveries and advances.
Among the many areas of research it is enabling is the study of resolved stellar populations (RSTs), which was the subject of ERS 1334.
It refers to large groups of stars that are close enough that individual stars can be discerned, but far enough away that telescopes can capture many of them at once. A good example is the Wolf-Lundmark-Melotte (WLM) dwarf galaxy from the Milky Way.
Kristen McQuinn, assistant professor of astrophysics at Rutgers University, is one of the principal scientists of the Webb ERS program whose work focuses on RSTs. He recently spoke with NASA Senior Communications Specialist Natasha Piro about how the JWST has enabled new studies of the WLM.
Webb’s improved observations have revealed that this galaxy has not interacted with other galaxies in the past.
According to McQuinn, this makes it a great candidate for astronomers to test theories about galaxy formation and evolution. Here are the highlights of this interview.
As for WLM
The WLM is about 3 million light-years from Earth, which means it’s pretty close (in astronomical terms) to the Milky Way. However, it is also relatively isolated, leading astronomers to conclude that it has not interacted with other systems in the past.
When astronomers have observed other nearby dwarf galaxies, they have noticed that they are usually entangled with the Milky Way, indicating that they are in the process of merging.
This makes them more difficult to study, as their population of stars and gas clouds is completely indistinguishable from ours.
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Another important thing about the WLM is that it is low in elements heavier than hydrogen and helium (which were very common in the early Universe). Elements such as carbon, oxygen, silicon, and iron formed in the cores of the first population stars and were dispersed when those stars exploded in supernovae.
In the case of WLM, which has experienced star formation throughout its history, the force of these explosions has pushed these elements over time. This process is known as “galactic winds” and has been observed with small, low-mass galaxies.
JWST images
Webb’s new images provide the clearest view of WLM ever seen. The dwarf galaxy was previously imaged by the Infrared Array Camera (IAC) on the Spitzer Space Telescope (SST).
These provided limited resolution compared to the Webb images, which can be seen in the side-by-side comparison (shown below).
A portion of the Wolf–Lundmark–Melotte (WLM) dwarf galaxy captured by the Spitzer Space Telescope’s infrared camera (left) and the James Webb Space Telescope’s near-infrared camera (right). (NASA, ESA, CSA, IPAC, Kristen McQuinn (RU)/Zolt G. Levay (STScI), Alyssa Pagan (STScI))
As you can see, Webb’s infrared optics and advanced suite of instruments provide a much deeper view that makes it possible to differentiate individual stars and features. As McQuinn described it:
“We can see countless individual stars of different colors, sizes, temperatures, ages and stages of evolution; interesting clouds of nebular gas within the galaxy; foreground stars with Webb diffraction spikes; and background galaxies with neat features like tidal tails. It’s really a beautiful picture.”
The ERS program
As McQuinn explained, the main science goal of ERS 1334 is to build on previous experience developed with Spitzer, Hubble and other space telescopes to learn more about the history of star formation in galaxies.
Specifically, they are performing multiband deep imaging of three star systems resolved within a Megaparsec (~3,260 light-years) of Earth using Webb’s Near Infrared Camera (NIRCam) and the Slitless Imaging Spectrograph near infrared (NIRISS).
These include the globular cluster M92, the ultra-dim dwarf galaxy Draco II and the star-forming dwarf galaxy WLM.
The population of low-mass stars in the WLM makes it particularly interesting because they are so long-lived, meaning that some of the stars seen there today could have formed during the early Universe.
“By determining the properties of these low-mass stars (such as their ages), we can gain insight into what was happening in the very distant past,” McQuinn said.
“It’s very complementary to what we learn about early galaxy formation by looking at high-redshift systems, where we see galaxies as they existed when they first formed.”
Another goal is to use the WLM dwarf galaxy to calibrate JWST to ensure it can measure the brightness of stars with extreme precision, allowing astronomers to test models of stellar evolution in the near-infrared.
McQuinn and colleagues are also developing and testing non-proprietary software to measure the brightness of resolved stars captured with the NIRCam, which will be made publicly available.
The results of your ESR project will be published before the cycle 2 call for proposals (January 27, 2023).
The James Webb Space Telescope has been in space for less than a year, but it’s already proven invaluable. The stunning views of the cosmos it has provided include deep-field imaging, extremely precise observations of galaxies and nebulae, and detailed spectra of the atmospheres of extrasolar planets.
The scientific advances it has already enabled have been nothing short of groundbreaking. Before its planned 10-year mission ends (which could be extended to 20), some truly paradigm-shifting advances are in store.
This article was originally published by Universe Today. Read the original article.