A team of astronomers, led by the Center for Astrophysics | Harvard and Smithsonian, has utilized galactic archaeology to trace the history of a galaxy outside the Milky Way for the first time.
The study, published in Nature Astronomy, introduces "extragalactic archaeology" as a new method to reconstruct the evolution of distant galaxies.
Methodology
- Researchers examined the nearby spiral galaxy NGC 1365 using data from the TYPHOON survey on the Irénée du Pont telescope.
- They achieved high resolution, allowing them to study individual star-forming clouds within the galaxy.
- The method involves analyzing the chemical fingerprints, specifically oxygen patterns, in the gas of the galaxy.
- Young, hot stars emit ultraviolet light, exciting nearby gases. Each element, like oxygen, then produces distinct light lines.
- Galactic centers typically show higher concentrations of heavy elements, including oxygen, compared to outer regions. This pattern is influenced by star formation, supernovae, gas flows, and past galaxy mergers.
Findings
- By comparing observed oxygen patterns in NGC 1365 with state-of-the-art galaxy simulations from the Illustris Project, astronomers inferred the galaxy's merger and growth history over 12 billion years.
- A simulation closely matching NGC 1365's properties was identified from approximately 20,000 galaxy simulations.
- The central region of NGC 1365 formed early and developed significant oxygen content.
- The outer gas accumulated over 12 billion years through collisions with smaller dwarf galaxies.
- The outer spiral arms likely formed more recently, within the last few billion years, also fueled by gas and stars from merging dwarf galaxies.
Significance
The study demonstrates that chemical fingerprints in a galaxy's gas can reveal its historical development.
- It establishes extragalactic archaeology as a powerful new astronomical tool.
- The research highlights the crucial collaboration between theoretical modeling and observational data.
- By studying galaxies like NGC 1365, which shares similarities with the Milky Way, astronomers can gain insights into the formation pathways of spiral galaxies and determine if our own galaxy is typical or unique.