Galaxy Formation and Evolution

Spiral galaxies often exist in isolation, while elliptical galaxies tend to cluster together. This observation suggests that galaxy morphology is linked to the surrounding environment, potentially due to increased interaction in denser regions.

Active galaxies exhibit additional non-stellar radiation originating from their nuclei, called active galactic nuclei (AGNs). This emission is likely driven by matter falling into a supermassive black hole at the galaxy's core.

Redshift is a phenomenon where light from distant objects appears shifted towards longer wavelengths (redder). This shift is caused by the expansion of the Universe, which stretches the light waves.

Galaxies at high redshifts are effectively 'snapshots' of galaxies in the early Universe. Studying the distribution and properties of these galaxies helps us understand how galaxies evolved over cosmic time.

The process of galaxy formation and evolution involves a complex interplay of gravitational collapse, gas accretion, star formation, and feedback mechanisms. This process shapes the structure and properties of galaxies over billions of years.

The formation of galaxies is a gradual process influenced by various factors including gravitational collapse, gas accretion, and feedback mechanisms. This process involves a balance between gravitational forces pulling matter together and pressure from stars and radiation pushing back, ultimately shaping the structure and properties of galaxies.

As galaxies evolve, they undergo changes in their properties, such as their morphology, stellar content, and gas content. These changes are driven by a variety of processes, including mergers, interactions with other galaxies, and star formation.

The study of high-redshift galaxies, which are essentially windows into the early Universe, helps us understand the formation and evolution of galaxies. Comparing these early galaxies to present-day galaxies, we can trace their growth and transformation throughout cosmic history.

The theory that the Universe is spatially homogeneous and isotropic, meaning that it looks the same in all directions and at all locations on large scales.

The study of the properties of spacetime on large scales, governing the evolution and structure of the Universe.

A model that describes the evolution of the Universe based on the Cosmological Principle and Einstein's theory of General Relativity.

A measure of how the length scales of the Universe are changing over time.

A measure of the curvature of spacetime. A value of K=0 indicates a flat universe, K>0 a closed universe, and K<0 an open universe.

The initial conditions and constraints imposed by the standard model of cosmology, which shape the formation of galaxies.

The process where gravitational forces from a larger galaxy pull material (dark matter, gas, stars) away from a smaller satellite galaxy.

The removal of gas from a satellite galaxy as it moves through the hot gas of a larger galaxy's halo. This happens when the drag force from the hot gas exceeds the satellite's gravitational hold on its gas.

Merging galaxies of similar mass often result in an elliptical galaxy, regardless of their initial shapes (spirals or ellipticals).

Elliptical galaxies are thought to form primarily through mergers of smaller galaxies over time.

A dynamic instability present in thin, dense disk galaxies that can lead to the formation of a bar-like structure within the galaxy.

A central bulge in a galaxy that forms due to the buckling of a bar structure, which results in a more rounded, ellipsoidal shape.

The evolution of a galaxy through interactions with other galaxies, gas, dark matter, and internal instabilities.

The process of a galaxy shedding mass and angular momentum due to external forces and internal instabilities.

The process of how a galaxy changes over time due to internal dynamics, such as the formation of bars and bulges.

The central, spheroidal component of a spiral galaxy, often containing older, redder stars.

Elements heavier than Helium, essential for understanding galaxy evolution and properties.

The abundance of metals in a celestial object, like a star or galaxy.

The process of how the chemical composition of a galaxy changes over time, driven by stellar evolution and the creation of heavier elements.

The interstellar medium is enriched with metals from stellar winds and supernova explosions.

The amount of starlight absorbed by dust grains in a galaxy, impacting its observed brightness.

The initial mass function (IMF) influences the mass and composition of stellar ejecta, impacting galaxy chemical evolution.

The Big Bang model predicts that the universe began in a hot, dense state and has been expanding ever since.

A process of nuclear fusion in the early universe that produced light elements like helium, deuterium, and lithium.

A measurement of the early universe that shows a nearly uniform background radiation, echoing the Big Bang.

The standard model of cosmology, which describes the evolution of the universe from the Big Bang to the present day.

The problem of how different parts of the universe, which were not causally connected in the early universe, ended up so similar.

The problem of explaining the flatness of the universe given that any deviation from flatness in the early universe would have been amplified over time.

The problem of explaining how the universe survived and evolved for so long, considering the extremely short time scales of physical processes in its early stages.

The problem of how the universe transitioned from an initial state of very high energy density to a more uniform and stable state.

A theory in particle physics that proposes a symmetry between bosons and fermions - each particle has a supersymmetric counterpart, implying that for every known particle, there exists a 'superpartner'.

A hypothetical particle predicted by supersymmetry models, considered a strong candidate for dark matter. It's neutral, weakly interacting, and massive, making it difficult to detect.

A theoretical type of dark matter where particles have a mass of about 1 keV, moving relatively slowly. This category includes particles like sterile neutrinos.

A theoretical type of dark matter where particles are very massive and move very slowly. This category includes particles like axions.

Cosmic Microwave Background (CMB) fluctuations are small variations in temperature across the early Universe's radiation. These fluctuations hold information about how the Universe evolved.

The process by which structures in the early Universe form, driven by gravity and initial density fluctuations. Gravity pulls denser regions together, forming stars, galaxies, and larger structures.

A model of structure formation that assumes the Universe is dominated by cold dark matter. This model predicts the formation of galaxies and explains the observed distribution of matter in the universe.

The theory that galaxies are not evenly distributed but are biased tracers of the dark matter density field, forming where the density is highest.