An international team led by Australia’s ASTRO 3D Research Center reports that age is a driving force in changing the motion of stars in galaxies. Galaxies begin their lives with an orderly rotation of stars, but in some the movement of stars is more chaotic. Until now, scientists didn’t know what caused this; maybe the environment or the mass of the galaxy.

Important findings about the age of the galaxy

A new study recently published MNRAS (Monthly Notices of the Royal Astronomical Society)) showed that the most important factor is neither one nor the other. This shows that the tendency for stars to move erratically depends largely on the age of the galaxy; Things get complicated over time.

“When we did the analysis, we found that no matter how we sliced ​​it, age was always the most important parameter,” says the study’s first author, ASTRO 3D researcher Professor Scott Croom from the University of Sydney.

Environmental and mass factors

“When you take age into account, there is actually no environmental bias, and the same goes for the audience.

“If you find a young galaxy, it will rotate in whatever environment it is in, and if you find an old galaxy, it will have more random orbits, whether in a dense environment or in a vacuum.”

Research group and methodology

The research team also included scientists from Macquarie University, Swinburne University of Technology, University of Western Australia, Australian National University, University of New South Wales, University of Cambridge, University of Queensland and Yonsei University in the Republic of Korea.

The study updates our understanding of previous studies that variously considered environment or mass to be more important factors. However, co-author Dr. Jesse van de Sande says the previous study wasn’t necessarily wrong.

Young galaxies are star-forming superfactories, while old galaxies stop star formation.

“We know that age is affected by the environment. If a galaxy falls into a dense environment, it tends to stop star formation. That’s why galaxies in denser environments are older on average, says Dr. van de Sande.

“The gist of our analysis is that it’s not living in a dense environment that reduces their return, but being older.”

Dynamics of the Milky Way

Our galaxy, the Milky Way, still has a thin star-forming disk, so it is still considered a high-spin spinning galaxy.

“But when we look at the Milky Way in detail, we see something called the thick disk of the Milky Way. It’s not dominant in terms of light, but it’s there, and these appear to be ancient stars that may have been heated from a thin disk at an earlier time or born by more turbulent motion in the early universe. ” says professor Krum.

Contribution of SAMI Galactic Research

Observation data made within the framework of the SAMI Galaxy Survey project were used in the study. The SAMI device was created in 2012 by the University of Sydney and the Anglo-Australian Observatory (now Astralis). SAMI uses the Anglo-Australian Telescope at Siding Spring Observatory near Coonabarabran, New South Wales. He studied 3,000 galaxies in a wide variety of environments. This research allows astronomers to ignore many processes when trying to understand the formation of galaxies, thus refining models of the evolution of the universe.

Future directions of galaxy research

The next steps will be to develop galaxy evolution simulations in more detail.

“One of the challenges of good modeling is the high resolution required to predict what is going on. “Typical current simulations are based on particles of around 100,000 stellar masses, and you cannot distinguish small-scale structures in the disks of galaxies,” says Professor Krum.

The investigation of the Hector galaxy will help Professor Krum and his team extend this work with the new instrument at the Anglo-Australian Telescope.

“Hector observes 15,000 galaxies, but with a higher spectral resolution, allowing the age and rotation of galaxies to be measured even in galaxies of much lower mass, providing more detailed information about the environment,” says Professor Julia Bryant, Hector’s project leader. Galaxy Research. University of Sydney.

Conclusion and impact on universal understanding

Professor Emma Ryan-Weber, Director of ASTRO 3D, said: “These discoveries answer one of the fundamental questions posed by ASTRO 3D: How do mass and angular momentum evolve in the universe?” This careful study by the SAMI team shows that the age of the galaxy determines the orbits of stars. “This important information contributes to a clearer picture of the universe.”