In cosmology, the study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, clustering and merging allows galaxies to accumulate mass, determining both their shape and structure. Hydrodynamics simulation, which simulates both baryons and dark matter, is widely used to study galaxy formation and evolution.
The rotation curve of a disc galaxy is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from each side are averaged to create the curve. A significant discrepancy exists between the experimental curves observed, and a curve derived by applying gravity theory to the matter observed in a galaxy. Theories involving dark matter are the main postulated solutions to account for the variance.
Rashid Alievich Sunyaev is a German, Soviet, and Russian astrophysicist of Tatar descent. He got his MS degree from the Moscow Institute of Physics and Technology (MIPT) in 1966. He became a professor at MIPT in 1974. Sunyaev was the head of the High Energy Astrophysics Department of the Russian Academy of Sciences, and has been chief scientist of the Academy's Space Research Institute since 1992. He has also been a director of the Max Planck Institute for Astrophysics in Garching, Germany since 1996, and Maureen and John Hendricks Distinguished Visiting Professor in the School of Natural Sciences at the Institute for Advanced Study in Princeton since 2010. In February 2022, he signed an open letter from Russian scientists and science journalists condemning Russia's invasion of Ukraine.
A galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of a galaxy comprise its halo:
The Lambda-CDM, Lambda cold dark matter, or ΛCDM model is a mathematical model of the Big Bang theory with three major components:
- a cosmological constant, denoted by lambda (Λ), associated with dark energy;
- the postulated cold dark matter, denoted by CDM;
- ordinary matter.
In modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has decoupled from cosmic expansion and contains gravitationally bound matter. A single dark matter halo may contain multiple virialized clumps of dark matter bound together by gravity, known as subhalos. Modern cosmological models, such as ΛCDM, propose that dark matter halos and subhalos may contain galaxies. The dark matter halo of a galaxy envelops the galactic disc and extends well beyond the edge of the visible galaxy. Thought to consist of dark matter, halos have not been observed directly. Their existence is inferred through observations of their effects on the motions of stars and gas in galaxies and gravitational lensing. Dark matter halos play a key role in current models of galaxy formation and evolution. Theories that attempt to explain the nature of dark matter halos with varying degrees of success include cold dark matter (CDM), warm dark matter, and massive compact halo objects (MACHOs).
The Millennium Run, or Millennium Simulation is a computer N-body simulation used to investigate how the distribution of matter in the Universe has evolved over time, in particular, how the observed population of galaxies was formed. It is used by scientists working in physical cosmology to compare observations with theoretical predictions.
Marc Davis is an American professor of astronomy and physics at the University of California, Berkeley. Davis received his bachelor's degree from the Massachusetts Institute of Technology in 1969, his Ph.D from Princeton University in 1973 and has been elected to both the National Academy of Sciences (1991) and the American Academy of Arts and Sciences (1992). He taught for a year at Princeton, 1973–74, then was on the astronomy faculty at Harvard from 1975 to 1981. Since 1981, he has been on the faculty of the Department of Astronomy and Physics at the University of California at Berkeley.
Carlos Silvestre Frenk is a Mexican-British cosmologist. Frenk graduated from the National Autonomous University of Mexico and the University of Cambridge and spent his early research career in the United States, before settling permanently in the United Kingdom. He joined the Durham University Department of Physics in 1986 and since 2001 has served as the Ogden Professor of Fundamental Physics at Durham University.
Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved, but the exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution and also provides astronomers with clues about how galaxies grew into their current forms over long stretches of time.
GADGET is free software for cosmological N-body/SPH simulations written by Volker Springel at the Max Planck Institute for Astrophysics. The name is an acronym of "GAlaxies with Dark matter and Gas intEracT". It is released under the GNU GPL. It can be used to study for example galaxy formation and dark matter.
The Navarro–Frenk–White (NFW) profile is a spatial mass distribution of dark matter fitted to dark matter halos identified in N-body simulations by Julio Navarro, Carlos Frenk and Simon White. The NFW profile is one of the most commonly used model profiles for dark matter halos. The substantial impact of NFW's work on theoretical understanding of cosmic structure formation can be traced to three key insights.
The Gruber Prize in Cosmology, established in 2000, is one of three prestigious international awards worth US$500,000 awarded by the Gruber Foundation, a non-profit organization based at Yale University in New Haven, Connecticut.
Julio F. Navarro FRSC is a professor of Astronomy at the department of Physics and Astronomy in the University of Victoria. Dr. Navarro's research is mainly focused on the formation and evolution of galaxies and galaxy clusters and the structure and evolution of their dark matter component. He is famous for his theoretical studies of dark matter halos carried out using massive N-body simulations. Julio F. Navarro along with Carlos Frenk and Simon White has formulated a density profile for dark matter halos, which was named after them. In 2015, he won the Henry Marshall Tory Medal of the Royal Society of Canada. He is chief editor of the journal Frontiers in Astronomy and Space Sciences.
Guinevere Alice Mei-Ing Kauffmann was born in California. She is an astrophysicist and is known for her work studying galaxies among other subjects.
The Virgo Consortium was founded in 1994 for Cosmological Supercomputer Simulations in response to the UK's High Performance Computing Initiative. Virgo developed rapidly into an international collaboration between a dozen scientists in the UK, Germany, Netherlands, Canada, United States and Japan.
George Petros Efstathiou is a British astrophysicist who is Professor of Astrophysics (1909) at the University of Cambridge and was the first director of the Kavli Institute for Cosmology at the University of Cambridge from 2008 to 2016. He was previously Savilian Professor of Astronomy at the University of Oxford.
The Institute for Computational Cosmology (ICC) is a research institute at Durham University, England. It was founded in November 2002 as part of the Ogden Centre for Fundamental Physics, which also includes the Institute for Particle Physics Phenomenology (IPPP). The ICC's primary mission is to advance fundamental knowledge in cosmology. Topics of active research include: the nature of dark matter and dark energy, the evolution of cosmic structure, the formation of galaxies, and the determination of fundamental parameters.
The Illustris project is an ongoing series of astrophysical simulations run by an international collaboration of scientists. The aim is to study the processes of galaxy formation and evolution in the universe with a comprehensive physical model. Early results were described in a number of publications following widespread press coverage. The project publicly released all data produced by the simulations in April, 2015. Key developers of the Illustris simulation have been Volker Springel and Mark Vogelsberger. The Illustris simulation framework and galaxy formation model has been used for a wide range of spin-off projects, starting with Auriga and IllustrisTNG followed by Thesan (2021), MillenniumTNG (2022) and TNG-Cluster (2023).
The UniverseMachine is a project carrying out astrophysical supercomputer simulations of various models of possible universes, created by astronomer Peter Behroozi and his research team at the Steward Observatory and the University of Arizona. Numerous universes with different physical characteristics may be simulated in order to develop insights into the possible beginning and evolution of our universe. A major objective is to better understand the role of dark matter in the development of the universe. According to Behroozi, "On the computer, we can create many different universes and compare them to the actual one, and that lets us infer which rules lead to the one we see."
