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Two images showing a portion of the WLM galaxy, one captured by NASA’s Hubble Space Telescope (left) and the other 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 its James Webb Space Telescope. Credit: NASA/ESA/CSA/IPAC/Kristen McQuinn-Rutgers University
By utilizing extensive data sets obtained through NASA’s James Webb Space Telescope, a research team led by a Rutgers University–New Brunswick astronomer is uncovering evidence of conditions present in the early universe. The team has analyzed the ages of stars in the Wolf–Lundmark–Melotte (WLM) galaxy, providing the most detailed depiction of it to date. This galaxy, situated near the Milky Way, is a hub of star formation and contains ancient stars formed approximately 13 billion years ago.
Kristen McQuinn, an assistant professor in the Department of Physics and Astronomy at the School of Arts and Sciences, led the research presented in The Astrophysical Journal. According to McQuinn, the team’s ability to delve deeply into the galaxy’s history of stellar development was made possible by the Amarel high-performance computing cluster managed by the Rutgers Office of Advanced Research Computing. The extensive computational effort also facilitated the validation of telescope calibrations and data processing procedures, benefitting the broader scientific community.
Low mass galaxies, such as WLM, are particularly intriguing to McQuinn because they are believed to have dominated the early universe. These galaxies offer researchers insight into star formation, the evolution of chemical elements, and the influence of star formation on a galaxy’s gas and structure. With advanced telescopes like the Webb, scientists are gaining a closer view of these faint and scattered galaxies, which make up the majority of galaxies in the local universe.
Discovered by Max Wolf in 1909 and further characterized by Knut Lundmark and Philibert Jacques Melotte in 1926, WLM is an “irregular” galaxy lacking a distinct shape like a spiral or ellipse. Positioned at the periphery of the Local Group—a group of galaxies including the Milky Way—WLM has been shielded from the effects of interacting with other galaxies, preserving its pristine star population. Additionally, WLM is attractive to astronomers due to its dynamic, complex nature and abundant gas, which supports active star formation.
To establish the galaxy’s star formation history, McQuinn’s team employed the telescope to meticulously focus on sections of the sky containing hundreds of thousands of individual stars. By assessing the color and brightness of stars to determine their age, the researchers were able to map out the rate at which stars were born across various epochs of the universe’s history. This meticulous cataloging revealed fluctuations in WLM’s star-forming capabilities over time. The team’s observations, consistent with earlier assessments using the Hubble Space Telescope, indicated that the galaxy underwent a period of star formation early in the universe’s history lasting 3 billion years, followed by a pause and then renewed star formation.
McQuinn suggested that the pause may have been influenced by specific conditions in the early universe, speculating that the universe’s high temperature caused the gas in WLM to heat up, temporarily inhibiting star formation. The subsequent period of cooling lasted for several billion years before star formation resumed once more. This research is part of NASA’s Early Release Program, where selected scientists collaborate with the Space Telescope Science Institute to showcase Webb’s capabilities and aid astronomers in preparing for future observations. Launched in December 2021, the Webb telescope, orbiting the sun a million miles away from Earth, offers scientists the opportunity to study a wide range of topics, including the early universe, the solar system’s history, and the search for exoplanets.
“We are expecting a plethora of new scientific discoveries from this program,” McQuinn stated. Other Rutgers researchers involved in the study included Max Newman, a doctoral student, and Roger Cohen, a postdoctoral associate, both from the Department of Physics and Astronomy at Rutgers School of Arts and Sciences.
More information:
Kristen. B. W. McQuinn et al, The JWST Resolved Stellar Populations Early Release Science Program. IV. The Star Formation History of the Local Group Galaxy WLM, The Astrophysical Journal (2024). DOI: 10.3847/1538-4357/ad1105
Journal information:
Astrophysical Journal
