Galaxy Formation and Evolution

The study of galaxies and their formation processes, covering various topics like star formation, dark matter, and the universe's size and age.

The formation of stars is an essential part of galaxy formation.

Dark Matter is a hypothetical form of matter that does not interact with light, making up a significant proportion of the universe.

The Big Bang Theory describes the origin and evolution of the universe, providing a framework for understanding galaxy formation.

The distribution of matter in the universe, which is crucial for understanding galaxy formation.

The process of gas collapsing under its own gravity to form stars, a key aspect of galaxy formation.

The evolution of stars over their lifespan, influencing the evolution of galaxies.

The process by which galaxies change over time due to interactions, mergers, and star formation activities.

Galaxies characterized by a smooth, elliptical shape, with little or no visible disk structure.

Galaxies with a prominent, flat disk structure and spiral arms.

A classification scheme that categorizes galaxies based on their shape, ranging from predominantly elliptical to predominantly disk-shaped.

A central, bulging region within spiral galaxies, often containing older, redder stars.

Galaxies with a dominant ellipsoidal component and a small disk.

Small, faint galaxies that typically do not follow the Hubble Sequence.

Dwarf galaxies with significant amounts of gas and ongoing star formation, often having an irregular shape.

Dwarf galaxies with little gas and no young stars, appearing very diffuse.

Galaxy formation involves applying known physics principles to the initial and boundary conditions of the universe.

Galaxy formation and evolution processes happen across a vast range of sizes and time scales, from the scale of the entire universe down to individual stars.

The study of galaxy evolution relies on observations of galaxies at different distances, which correspond to different epochs in the universe's history.

Galaxies exhibit various scaling relations, meaning their structural parameters are linked by predictable relationships, providing insight into their formation.

Galaxies are used as markers to study the evolution of the universe as a whole because they are bright, long-lived, and can be observed across vast distances.

The study of galaxy formation and evolution is unique because it involves extremely long time scales, beyond human observation.

The finite speed of light allows us to view distant galaxies as they were in the past, providing data for understanding their evolution.

By observing and analyzing the properties of galaxies at different distances, we can infer how they have evolved over time.

The radius that encloses a specific fraction of a galaxy's total luminosity.

The brightness of a galaxy per unit area.

The ratio of a galaxy's cold gas mass to its total mass (cold gas + stars).

The color of a galaxy based on its luminosity in different wavelengths of light.

Disk galaxies are supported by rotation, and their sizes are a measure of their specific angular momentum (see Chapter 11)

Elliptical galaxies are supported by random motions, and their sizes reflect the amount of dissipation during their formation (see Chapter 13).

The distribution of galaxy sizes holds important information about their formation and evolution.

Elliptical galaxies typically have very low gas mass fractions, while disk galaxies have higher fractions, with the lowest surface brightness disk galaxies having the most gas.

The process of a larger dark matter halo forming from the merging of smaller progenitor halos.

A diagram depicting the merger history of a dark matter halo, showing its progenitors at different epochs.

The process by which the orbital energy of merging halos is quickly converted into binding energy, resulting in a single, more stable halo.

A smooth accretion process where larger halos grow by merging with numerous smaller halos.

Gas associated with merging halos is heated by shock waves and settles into a new equilibrium within the merged halo.

The process where a smaller halo orbits within a larger halo, eventually spiraling inwards due to dynamical friction.

The force that removes mass from the outer regions of a smaller halo as it orbits within a larger halo.

The process by which merging galaxies form a new, central galaxy in the resulting halo.

The process by which the chemical composition of gas and stars in galaxies changes over time, primarily due to stellar evolution and the release of heavy elements into the interstellar medium (ISM).

The amount of heavy elements, collectively called metals, in a given component of a galaxy, expressed as a fraction of its total mass.

The first three minutes of the Universe after the Big Bang, during which the abundance of elements was established.

Materials found in stars, heavier than helium, formed during stellar evolution.

Areas between stars, enriched by heavy elements released during stellar life cycles.

Small solid particles composed of heavy elements, found in interstellar gas and responsible for absorbing and re-emitting starlight.

The birth, life, and death of stars, a fundamental process impacting galaxy evolution.