The Milky Way has long and fascinating history that extends back to early Universe ca 13.61 billion years before.
It has evolve and merged with other galaxies to become the galaxy we see today.
In latest study a team of Canadian astronomers has created the detailed reconstruction of how the Milky Way evolved from its earliest phase to current phase.
Using data provided by the James Webb Space Telescope JWST the team examined 877 galaxies whose masses properties closely match what astronomers expect the Milky Way looked like over time.
Astrophysics
The galaxies in this survey spanned range of cosmic time from when the Universe was1.5 to 10 billion years old.
By observing more galaxies that existed when the Universe was younger the team created a visual timeline of Milky Way evolution.
To their surprise they found that Milky Way had remarkably turbulent youth before setting into stable and structure adult we are familiar with today.
In accordance with the Hubble Sequence astronomers classify galaxies into three groups based on their shapes spiral, elliptical and barred spiral.
Elliptical galaxies represent early phase of evolution and have structure or interstellar dust and gas.
Lenticulars which represent intermediate phase in evolution consist of bright central bulge surrounded by extended disk, spiral noted for their pinwheel form, consist of central bulge and flattened disk with stars shaping spiral structure.
Outside of these three morphologies are famous as irregular galaxies.
The study was led by Dr Vivian Tan who completed her PhD at York University under supervision of Prof. Adam Muzzin.
Astrophysics
They were joined by researchers from Dunlap Institute of Astronomy and Astrophysics, the SMU Institute for Computational Astrophysics, the Kapteyn Astronomical Institute, the Columbia Astrophysics Laboratory, the Space Telescope Science Institute.
The galaxies in sample are dated to crucial epoch when galaxies went from being smaller, masses of stars to stable disk galaxies that are common today.
For their study, the team combined high resolution imaging from the JWST and venerable Hubble to create census of 877 early galaxies.
The JWST observation were obtained as part of the Canadian NIRISS Unbiased Cluster Survey CANUCS.
This Canadian observing program uses data from Webb Near Infrared Imager and Slitless Spectrograph NIRISS.
This instrument was built by Canadian Space Agency CSA in partnership with the Universite de Montreal the National Research Council Herzberg Centre for Astronomy and Astrophysics, and Honeywell Robotics, CANUCS uses data from the NIRISS instrument to observe five galaxy clusters which are natural gravitational lenses that allow astronomers to observe fainter more galaxies.
Mixed with visible light observations by Hubble the team created resolved stellar mass and star formation SFR maps for each galaxy observed.
These maps showed where existing stars were located.
New stars were forming during different phases of galaxies evolution.
The results showed a clear pattern across entire sample showing that Milky Way Galaxy twins grew from the inside out between 3 and 4 billion years after Big Bang.
Galaxy
They start with dense central region and mass in their outer regions through mergers and new star formation gradually forming extended spiral structures.
Tan and her colleagues then ran state of the art computer simulations that track the evolution of Milky Way like galaxies which confirmed inside out growth model they observed.
The simulation failed to reproduce the high central nature of early galaxies in some cases and failed to predict how mass accumulated in outer regions.
These results provide constrains for theoretical models of evolution and mechanism involved including feedback merger rates.
Astronomers have been modeling the formation of the Milky Way and spiral galaxies for decades said Tan.
It is amazing that with the JWST we can test their models and map out how Milky Way progenitors grow with Universe itself.
A major takeaway from this study is pointed that Milky Way early history was more chaotic than previously expected.
It appear galaxies in early time were constantly celliding and accreting material triggering intense bursts so star formation.
Galaxy
This is evidence by highly disturbed shapes and asymmetric features they observed.
Milky Way twins appear much more stable in later cosmological times characterized by smoother structures and more distributed star formation.
