The James Webb Space Telescope Early Release Science (ERS) program – first released on July 12, 2022 – has proven to be a treasure trove of scientific discoveries and breakthroughs.
Among the many areas of research it enables is the study of Resolved Stellar Populations (RST), which was the subject of ERS 1334.
This refers to large groups of stars close enough that individual stars can be distinguished but far enough apart that telescopes can capture many of them at once. A good example is the dwarf galaxy Wolf-Lundmark-Melotte (WLM) which borders the Milky Way.
Kristen McQuinn, assistant professor of astrophysics at Rutgers University, is one of the lead scientists in the Webb ERS program whose work is focused on RST. Recently, she spoke with Natasha Piro, a NASA senior communications specialist, about how 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 an excellent candidate for astronomers to test theories of galaxy formation and evolution. Here are the highlights of that interview.
Regarding WLM
The WLM is about 3 million light years from Earth, which means it’s pretty close (in astronomical terms) to the Milky Way. But it is also relatively isolated, leading astronomers to conclude that it has not interacted with other systems before.
When astronomers have observed other nearby dwarf galaxies, they have noticed that they are usually entangled with the Milky Way, indicating that they are merging.
This makes them more difficult to study because their population of stars and gas clouds is indistinguishable from our own.
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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 were formed in the cores of early population stars and dispersed when these stars exploded in supernovae.
In the case of the WLM, which has experienced star formation throughout its history, the force of these explosions has driven these elements out over time. This process is known as “galactic winds” and has been observed with small, low-mass galaxies.
JWST images
The new Webb images provide the clearest picture of WLM ever seen. Previously, the dwarf galaxy was imaged by the Infrared Array Camera (IAC) on the Spitzer Space Telescope (SST).
These provided limited resolution compared to the Web images, as can be seen in the side-by-side comparison (shown below).
As you can see, Webb’s infrared optics and advanced suite of instruments provide a much deeper picture that makes it possible to distinguish individual stars and features. As McQuinn described it:
“We can see a myriad of individual stars of different colors, sizes, temperatures, ages and stages of evolution; interesting clouds of nebular gas in the galaxy; foreground stars with Webb diffraction spikes; and background galaxies with neat features like tidal tails. It’s really a wonderful picture.”
ERS program
As McQuinn explained, the main science focus of ERS 1334 is to build on previous expertise developed with Spitzer, Hubble and other space telescopes to learn more about the star formation history of galaxies.
Specifically, they are performing deep multiband imaging of three resolved star systems within a Megaparsec (~3,260 light-years) of Earth using Webb’s Near-Infrared Camera (NIRCam) and Near-Infrared Imaging Slitless Spectrograph (NIRISS).
These include the globular cluster M92, the ultra-faint 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 may 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 happened in the very distant past,” McQuinn said.
“It’s very complementary to what we’re learning about the early formation of galaxies by looking at high-redshift systems, where we see the galaxies as they were 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 accuracy, allowing astronomers to test stellar evolution models in the near-infrared.
McQuinn and her colleagues are also developing and testing non-proprietary software to measure the brightness of resolved stars imaged with NIRCam, which will be made available to the public.
The results of their ESR project will be released 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 has already proven invaluable. The breathtaking views of the cosmos it has provided include deep-field images, extremely precise observations of galaxies and nebulae, and detailed spectra of extrasolar planetary atmospheres.
The scientific breakthroughs it has already allowed have been nothing short of groundbreaking. Before its planned 10-year mission is over (which could be extended to 20), some truly paradigm-shifting breakthroughs are expected.
This article was originally published by Universe Today. Read the original article.
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