This nearby dwarf galaxy has been lonely for almost the entire age of the universe

This nearby dwarf galaxy has been lonely for almost the entire age of the universe

The James Webb Space Telescope Early Release Science (ERS) program – first launched on July 12, 2022 – has proven to be a treasure trove of discoveries and scientific 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 discerned but far enough away that telescopes can capture several at once. A good example is the Wolf-Lundmark-Melotte (WLM) dwarf galaxy neighboring the Milky Way.

Kristen McQuinn, assistant professor of astrophysics at Rutgers University, is one of the leading scientists in the Webb ERS program whose work focuses on RST. Recently, she spoke to Natasha Piro, a senior NASA communications specialist, about how JWST has enabled new studies of WLM. WebbEnhanced observations of 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 this interview:

About WLM

The WLM is about 3 million light-years from Earth, which means it’s quite 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 observed other nearby dwarf galaxies, they noticed that they are usually entangled with the Milky Way, indicating that they are merging. This makes them more difficult to study since their population of stars and gas clouds cannot be entirely distinguished 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 early population stars and were dispersed when those stars exploded into supernovae. In the case of WLM, which has experienced star formation throughout its history, the force of these explosions has repelled these elements 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 view of WLM ever. Previously, the dwarf galaxy was photographed by the Infrared Camera (IAC) on the Spitzer Space Telescope (OHS). These provided limited resolution compared to the Webb images, which can be seen in the side-by-side comparison (below). As you can see, Webb’s infrared optics and suite of advanced instruments provide a much deeper view that can differentiate between stars and individual 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 really is a magnificent image.

Side-by-side comparison of images taken from WLM by Spitzer and Webb. Credit: NASA/ESA/CSA/ STScI/Kristen McQuinn (Rutgers University)/Alyssa Pagan (STScI)

The ERS program

As McQuinn explained, the main scientific objective of ERS 1334 is to build on previous expertise developed with Spitzer, Hubble, and other space telescopes to learn more about the history of star formation in galaxies. Specifically, they achieve deep multiband imaging of three resolved star systems within one megaparsec (~3,260 light-years) of Earth using WebbNear 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 WLM makes it particularly interesting because they are long-lived, meaning some of the stars seen there today may have formed early in the Universe. . “By determining the properties of these low-mass stars (like their age), 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 systems, where we see 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 star brightness with extreme precision, which will allow astronomers to test models of stellar evolution in the near future. infrared. McQuinn and his colleagues are also developing and testing non-proprietary software to measure 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 published before the Round 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 he provided include deep-field images, extremely precise observations of galaxies and nebulae, and detailed spectra of extrasolar planet atmospheres. The scientific breakthroughs it has already enabled have been nothing short of revolutionary. Before the end of its planned ten-year mission (which could be extended to twenty years), truly revolutionary breakthroughs are expected.

Further Reading: NASA Blogs

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