February 26, 2024

Research reveals clues about conditions in the early universe

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Two views of a portion of the WLM galaxy, one taken by NASA’s Hubble Space Telescope (left), the second by the James Webb Space Telescope. Credit: NASA/ESA/CSA/IPAC/Kristen McQuinn-Rutgers University

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Two views of a portion of the WLM galaxy, one taken by NASA’s Hubble Space Telescope (left), the second by the James Webb Space Telescope. Credit: NASA/ESA/CSA/IPAC/Kristen McQuinn-Rutgers University

Employing massive data sets collected via NASA’s James Webb Space Telescope, a research team led by a Rutgers University–New Brunswick astronomer is unearthing clues about conditions that existed in the early universe.

The team cataloged the ages of stars in the Wolf-Lundmark-Melotte (WLM) galaxy, building the most detailed picture of it yet, according to the researchers. WLM, a neighbor of the Milky Way, is an active center of star formation that includes ancient stars formed 13 billion years ago.

“By looking so deeply and seeing so clearly, we can – effectively – go back in time,” said Kristen McQuinn, assistant professor in the Department of Physics and Astronomy in the School of Arts and Sciences, who led the study. research, described in The Astrophysical Journal. “Basically, you’re doing a kind of archaeological dig, to find very low-mass stars that formed early in the history of the universe.”

McQuinn credited the Amarel high-performance computing cluster managed by the Rutgers Office of Advanced Research Computing for allowing the team to calculate the galaxy’s stellar development history. One aspect of the research involved making a massive calculation and repeating it 600 times, McQuinn said.

The large computational effort also helped confirm telescope calibrations and data processing procedures that will benefit the broader scientific community, she added.

So-called “low-mass” galaxies are of special interest to McQuinn. Because they are believed to have dominated the early universe, they allow researchers to study star formation, the evolution of chemical elements and the impact of star formation on the gas and structure of a galaxy. Tensile and spread across the sky, they make up the majority of galaxies in the local universe. Advanced telescopes like Webb are allowing scientists a more detailed look.

WLM – an “irregular” galaxy, meaning it does not have a distinct shape such as a spiral or ellipse – was discovered by German astronomer Max Wolf in 1909 and characterized in more detail in 1926 by Swedish astronomer Knut Lundmark and British astronomer Philibert Jacques Melotte. It is positioned on the outskirts of the Local Group, a dumbbell-shaped group of galaxies that includes the Milky Way.

Being on the edge of the Local Group protected WLM from the ravages of mixing with other galaxies, leaving its stellar population in a pristine state useful for study, McQuinn noted. The WLM is also interesting to astronomers because it is a dynamic and complex system with a lot of gas, which allows it to actively form stars.

To formulate the galaxy’s star formation history – the rate at which stars were born at different times in the universe – McQuinn and his team used the telescope to carefully focus on swaths of the sky containing hundreds of thousands of individual stars. To determine the age of a star, they measured its color – an indicator of temperature – and its brightness.

“We can use what we know about stellar evolution and what these colors and brightnesses indicate to basically age the stars in the galaxy,” McQuinn said, adding that the researchers counted stars of different ages and mapped the stars’ birth rate over the course of the galaxy. of Earth’s history. the universe. “What you end up getting is a sense of how old this structure you’re looking at is.”

Cataloging the stars this way showed researchers that WLM’s star-making capabilities ebbed and flowed over time. The team’s observations, which confirm previous assessments made by scientists using the Hubble Space Telescope, show that the galaxy produced stars early in the history of the Universe, over a period of 3 billion years. It stopped for a while and then started again.

McQuinn said he believes the pause was caused by conditions specific to the early universe.

“The universe at that time was very hot,” she said. “We think that the temperature of the Universe ended up heating the gas in this galaxy and shut down star formation for a while. The cooling period lasted a few billion years and then star formation continued again.”

The research is part of NASA’s Early Launch Program, where assigned scientists work with the Space Telescope Science Institute and conduct research designed to highlight Webb’s capabilities and help astronomers prepare for future observations.

NASA launched the Webb Telescope in December 2021. The large, mirror-like instrument orbits the Sun a million miles away from Earth. Scientists compete for time at the telescope to study a range of topics, including conditions in the early universe, the history of the solar system and the search for exoplanets.

“There’s a lot of science that will come out of this program that hasn’t been done yet,” McQuinn said.

Other Rutgers researchers involved in the study included Max Newman, a doctoral student, and Roger Cohen, a postdoctoral associate, both in the Department of Physics and Astronomy at the Rutgers School of Arts and Sciences.

More information:
Kristen. BW McQuinn et al, Scientific Program for Early Release of JWST-Resolved Stellar Populations. 4. The history of star formation of the local group Galaxy WLM, The Astrophysical Journal (2024). DOI: 10.3847/1538-4357/ad1105

Diary information:
Astrophysical Journal

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