Galaxy Formation
Let's delve into the intricate process of galaxy formation during the epoch 10 billion years
ago, a period characterized by intense activity and rapid evolution.
The Seeds of Galaxies:
● Dark Matter Halos:
○ The story begins with dark matter, a mysterious substance that makes up a
significant portion of the universe's mass.
○
○ Dark matter coalesced into vast, invisible structures called halos. These halos
provided the gravitational scaffolding for galaxy formation.
○
● Primordial Gas:
○ Within these dark matter halos, primordial gas, primarily hydrogen and helium
left over from the Big Bang, began to accumulate.
○
○ This gas was initially diffuse and relatively uniform.
The Formation Process:
● Gravitational Collapse:
○ The gravitational pull of the dark matter halo caused the gas to collapse
inward.
○ As the gas collapsed, it heated up and became denser.
● Disk Formation:
○ Due to the initial rotation of the gas, it settled into a rotating disk.
○
○ This disk became the birthplace of stars.
● Star Formation Bursts:
○ Within these disks, dense regions of gas began to collapse under their own
gravity, triggering bursts of star formation.
○ These young stars emitted intense radiation, further heating and ionizing the
surrounding gas.
○ Because of the high amounts of gas present, star formation happened at a
much higher rate than it does in modern galaxies.
● Early Galaxy Morphology:
○ Many of these early galaxies were irregular and clumpy, lacking the
well-defined spiral or elliptical shapes we see today.
○
○ They were often smaller and more chaotic than modern galaxies.
Collisions and Mergers:
● Frequent Interactions:
○ In the early universe, galaxies were closer together, making collisions and
mergers much more frequent.
○
○ These interactions played a crucial role in shaping galaxy morphology.
● Galaxy Evolution:
○ Mergers could trigger intense bursts of star formation, transforming irregular
galaxies into more organized structures.
○
○ Major mergers could also lead to the formation of elliptical galaxies, which are
characterized by their smooth, featureless appearance.
○
● Growth of Supermassive Black Holes:
○ Galaxy mergers also fueled the growth of supermassive black holes at the
centers of galaxies.
○
○ As galaxies collided, gas and dust were funneled into the central regions,
feeding the black holes and powering quasars.
Clustering and Large-Scale Structure:
● Filaments and Clusters:
○ Galaxies were not randomly distributed throughout the universe.
○
○ They tended to cluster together along filaments and in dense regions called
clusters.
○ These structures formed a vast cosmic web, a network of interconnected
galaxies and clusters.
● Hierarchical Formation:
○ The formation of large-scale structure followed a hierarchical pattern, with
smaller structures forming first and then merging to form larger ones.
○
○ This process continues to shape the distribution of galaxies in the universe
today.
Key Factors:
● Dark Matter: Provided the gravitational framework for galaxy formation.
●
● Gas Dynamics: The collapse and cooling of primordial gas.
● Star Formation: The creation of stars within galaxy disks.
● Galaxy Interactions: Collisions and mergers that shaped galaxy morphology.
● Cosmic Web: The large-scale distribution of galaxies in filaments and clusters.
●
In summary, 10 billion years ago, galaxy formation was a dynamic and chaotic process,
driven by gravity, gas dynamics, and frequent interactions. 1 This epoch laid the foundation
for the diverse array of galaxies we observe in the universe today.
By Sri
vr.srikumar@gmail.com
