Webb gives us a stunning new look at this lonely dwarf galaxy: ScienceAlert
The James Webb Space Telescope Early Release Science (ERS) program — first released on July 12, 2022 — has revealed a wealth of scientific finds and breakthroughs.
Among the many areas of research it allows is the study of Resolved Stellar Populations (RSTs), which has been the subject of ERS 1334.
This refers to large groups of stars that are close enough together to distinguish individual stars, but far enough apart that telescopes can capture many at once. A good example is the Wolf-Lundmark-Melotte (WLM) dwarf galaxy adjacent to the Milky Way.
Kristen McQuinn, an assistant professor of astrophysics at Rutgers University, is one of the lead scientists of the Webb ERS program whose work focuses on RSTs. Recently, she spoke with Natasha Piroa senior communications specialist from NASA, on how the JWST has enabled new studies of the WLM.
Webb’s improved observations have shown 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 that interview.
The WLM is about 3 million light-years from Earth, meaning it’s fairly 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 noted that they are typically entwined with the Milky Way, indicating that they are in the process of merging.
This makes them more difficult to study, because their populations of stars and gas clouds cannot be fully distinguished from ours.
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Another important aspect of WLM is that it contains few elements heavier than hydrogen and helium (which were common in the early universe). Elements such as carbon, oxygen, silicon and iron formed in the cores of early population stars and were scattered when these stars exploded in supernovae.
In the case of WLM, which has experienced star formation throughout its history, the force of these explosions pushed these elements out over time. This process is known as “galactic winds” and has been observed in small, bright galaxies.
These yielded limited resolution compared to the Webb images, which can be seen in the side-by-side comparison (shown below).
As you can see, Webb’s infrared optics and advanced instrument array provide a much deeper view allowing individual stars and features to be distinguished. As McQuinn put it:
“We can see a large number of individual stars of different colors, sizes, temperatures, ages and evolutionary stages; interesting clouds of nebula gas in the galaxy; foreground stars with Webb’s diffraction peaks; and background galaxies with nice features like tidal tails. It’s a really beautiful image.”
The ERS program
As McQuinn explained, the main scientific focus of ERS 1334 is building on previous expertise developed with Spitzer, Hubble and other space telescopes to learn more about the history of star formation in galaxies.
In particular, they perform deep multiband imaging of three resolved stellar systems within a Megaparsec (~3,260 light-years) from Earth using Webb’s Near infrared camera (NIRCam) and Near infrared imaging Slitless spectrograph (SOUNDS).
The population of low-mass stars in WLM makes it especially interesting because they live so long, meaning some of the stars we see 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 learn about early galaxy formation by looking at high redshift systemswhere we see the galaxies as they existed when they first formed.”
Another goal is to use the WLM dwarf galaxy to calibrate the JWST to ensure it can measure the brightness of stars with extreme accuracy, allowing astronomers to test star evolution models in the near infrared.
McQuinn and her colleagues are also developing and testing non-proprietary software for measuring the brightness of resolved stars imaged with the 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 itself invaluable. The breathtaking views of the cosmos it has provided include deep-field images, highly accurate observations of galaxies and nebulae, and detailed spectra of extrasolar planetary atmospheres.
The scientific breakthroughs it has already made possible were nothing short of groundbreaking. Before the planned 10-year mission is over (which can be extended to 20), some truly paradigm-shifting breakthroughs are expected.
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