Cold dark matter

Last updated

In cosmology and physics, cold dark matter (CDM) is a hypothetical type of dark matter. According to the current standard model of cosmology, Lambda-CDM model, approximately 27% of the universe is dark matter and 68% is dark energy, with only a small fraction being the ordinary baryonic matter that composes stars, planets, and living organisms. Cold refers to the fact that the dark matter moves slowly compared to the speed of light, giving it a vanishing equation of state. Dark indicates that it interacts very weakly with ordinary matter and electromagnetic radiation. Proposed candidates for CDM include weakly interacting massive particles, primordial black holes, and axions.

Contents

History

The theory of cold dark matter was originally published in 1982 by James Peebles; [1] while the warm dark matter picture was proposed independently at the same time by J. Richard Bond, Alex Szalay, and Michael Turner; [2] and George Blumenthal, H. Pagels, and Joel Primack. [3] A review article in 1984 by Blumenthal, Sandra Moore Faber, Primack, and Martin Rees developed the details of the theory. [4]

Structure formation

In the cold dark matter theory, structure grows hierarchically, with small objects collapsing under their self-gravity first and merging in a continuous hierarchy to form larger and more massive objects. Predictions of the cold dark matter paradigm are in general agreement with observations of cosmological large-scale structure.

In the hot dark matter paradigm, popular in the early 1980s but less so in the 1990s, structure does not form hierarchically (bottom-up), but forms by fragmentation (top-down), with the largest superclusters forming first in flat pancake-like sheets and subsequently fragmenting into smaller pieces like our galaxy the Milky Way.

Since the late 1980s or 1990s, most cosmologists favor the cold dark matter theory (specifically the modern Lambda-CDM model) as a description of how the universe went from a smooth initial state at early times (as shown by the cosmic microwave background radiation) to the lumpy distribution of galaxies and their clusters we see today—the large-scale structure of the universe. Dwarf galaxies are crucial to this theory, having been created by small-scale density fluctuations in the early universe; [5] they have now become natural building blocks that form larger structures.

Composition

Dark matter is detected through its gravitational interactions with ordinary matter and radiation. As such, it is very difficult to determine what the constituents of cold dark matter are. The candidates fall roughly into three categories:

Challenges

Several discrepancies between the predictions of cold dark matter in the ΛCDM model and observations of galaxies and their clustering have arisen. Some of these problems have proposed solutions, but it remains unclear whether they can be solved without abandoning the ΛCDM model. [15]

Cuspy halo problem

The density distributions of dark matter halos in cold dark matter simulations (at least those that do not include the impact of baryonic feedback) are much more peaked than what is observed in galaxies by investigating their rotation curves. [16]

Dwarf galaxy problem

Cold dark matter simulations predict large numbers of small dark matter halos, more numerous than the number of small dwarf galaxies that are observed around galaxies like the Milky Way. [17]

Satellite disk problem

Dwarf galaxies around the Milky Way and Andromeda galaxies are observed to be orbiting in thin, planar structures whereas the simulations predict that they should be distributed randomly about their parent galaxies. [18]

High-velocity galaxy problem

Galaxies in the NGC 3109 association are moving away too rapidly to be consistent with expectations in the ΛCDM model. [19] In this framework, NGC 3109 is too massive and distant from the Local Group for it to have been flung out in a three-body interaction involving the Milky Way or Andromeda Galaxy. [20]

Galaxy morphology problem

If galaxies grew hierarchically, then massive galaxies required many mergers. Major mergers inevitably create a classical bulge. On the contrary, about 80% of observed galaxies give evidence of no such bulges, and giant pure-disc galaxies are commonplace. [21] The tension can be quantified by comparing the observed distribution of galaxy shapes today with predictions from high-resolution hydrodynamical cosmological simulations in the ΛCDM framework, revealing a highly significant problem that is unlikely to be solved by improving the resolution of the simulations. [22] The high bulgeless fraction was nearly constant for 8 billion years. [23]

Fast galaxy bar problem

If galaxies were embedded within massive halos of cold dark matter, then the bars that often develop in their central regions would be slowed down by dynamical friction with the halo. This is in serious tension with the fact that observed galaxy bars are typically fast. [24]

Small-scale crisis

Comparison of the model with observations may have some problems on sub-galaxy scales, possibly predicting too many dwarf galaxies and too much dark matter in the innermost regions of galaxies. This problem is called the "small scale crisis". [25] These small scales are harder to resolve in computer simulations, so it is not yet clear whether the problem is the simulations, non-standard properties of dark matter, or a more radical error in the model.

High redshift galaxies

Observations from the James Webb Space Telescope have resulted in various galaxies confirmed by spectroscopy at high redshift, such as JADES-GS-z13-0 at cosmological redshift of 13.2. [26] [27] Other candidate galaxies which have not been confirmed by spectroscopy include CEERS-93316 at cosmological redshift of 16.7. Such a high rate of large galaxy formation in the early universe appears to contradict the rates of galaxy formation allowed in the existing Lambda CDM model via dark matter halos, as even if galaxy formation were 100% efficient and all mass were allowed to turn into stars in Lambda CDM, it wouldn't be enough to create such large galaxies. [28] [29] [30] However, this depends upon assuming a stellar initial mass function. If early star formation favored massive stars, this could explain the tension. [31]

See also

Related Research Articles

<span class="mw-page-title-main">Physical cosmology</span> Branch of cosmology which studies mathematical models of the universe

Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood.

In astronomy, dark matter is a hypothetical form of matter that appears not to interact with light or the electromagnetic field. Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be seen. Such effects occur in the context of formation and evolution of galaxies, gravitational lensing, the observable universe's current structure, mass position in galactic collisions, the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies.

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, that 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.

Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter.

<span class="mw-page-title-main">Galaxy rotation curve</span> Observed discrepancy in galactic angular momenta

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.

A MAssive Compact Halo Object (MACHO) is a kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos. A MACHO is a body that emits little or no radiation and drifts through interstellar space unassociated with any planetary system. Since MACHOs are not luminous, they are hard to detect. MACHO candidates include black holes or neutron stars as well as brown dwarfs and unassociated planets. White dwarfs and very faint red dwarfs have also been proposed as candidate MACHOs. The term was coined by astrophysicist Kim Griest.

A non-standard cosmology is any physical cosmological model of the universe that was, or still is, proposed as an alternative to the then-current standard model of cosmology. The term non-standard is applied to any theory that does not conform to the scientific consensus. Because the term depends on the prevailing consensus, the meaning of the term changes over time. For example, hot dark matter would not have been considered non-standard in 1990, but would have been in 2010. Conversely, a non-zero cosmological constant resulting in an accelerating universe would have been considered non-standard in 1990, but is part of the standard cosmology in 2010.

The cuspy halo problem is a discrepancy between the inferred dark matter density profiles of low-mass galaxies and the density profiles predicted by cosmological N-body simulations. Nearly all simulations form dark matter halos which have "cuspy" dark matter distributions, with density increasing steeply at small radii, while the rotation curves of most observed dwarf galaxies suggest that they have flat central dark matter density profiles ("cores").

The Lambda-CDM, Lambda cold dark matter, or ΛCDM model is a mathematical model of the Big Bang theory with three major components:

  1. a cosmological constant denoted by lambda (Λ) associated with dark energy
  2. the postulated cold dark matter denoted by CDM
  3. ordinary matter
<span class="mw-page-title-main">Dark matter halo</span> Theoretical cosmological structure

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.

<span class="mw-page-title-main">Satellite galaxy</span> Galaxy that orbits a larger galaxy due to gravitational attraction

A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy. Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within our own solar system are gravitationally bound to the Sun. While most satellite galaxies are dwarf galaxies, satellite galaxies of large galaxy clusters can be much more massive. The Milky Way is orbited by about fifty satellite galaxies, the largest of which is the Large Magellanic Cloud.

Warm dark matter (WDM) is a hypothesized form of dark matter that has properties intermediate between those of hot dark matter and cold dark matter, causing structure formation to occur bottom-up from above their free-streaming scale, and top-down below their free streaming scale. The most common WDM candidates are sterile neutrinos and gravitinos. The WIMPs, when produced non-thermally, could be candidates for warm dark matter. In general, however, the thermally produced WIMPs are cold dark matter candidates.

In astrophysics and particle physics, self-interacting dark matter (SIDM) is an alternative class of dark matter particles which have strong interactions, in contrast to the standard cold dark matter model (CDM). SIDM was postulated in 2000 as a solution to the core-cusp problem. In the simplest models of DM self-interactions, a Yukawa-type potential and a force carrier φ mediates between two dark matter particles. On galactic scales, DM self-interaction leads to energy and momentum exchange between DM particles. Over cosmological time scales this results in isothermal cores in the central region of dark matter haloes.

<span class="mw-page-title-main">Simon White</span> British astronomer

Simon David Manton White, FRS, is a British-German astrophysicist. He was one of directors at the Max Planck Institute for Astrophysics before his retirement in late 2019.

Modified Newtonian dynamics (MOND) is a hypothesis that proposes a modification of Newton's second law to account for observed properties of galaxies. It is supported by a minority of astrophysicists as an alternative to the more widely accepted hypothesis of dark matter in terms of explaining why galaxies do not appear to obey the currently understood laws of physics.

Stacy McGaugh is an American astronomer and professor in the Department of Astronomy at Case Western Reserve University in Cleveland, Ohio. His fields of specialty include low surface brightness galaxies, galaxy formation and evolution, tests of dark matter and alternative hypotheses, and measurements of cosmological parameters.

<span class="mw-page-title-main">Scalar field dark matter</span> Classical, minimally coupled, scalar field postulated to account for the inferred dark matter

In astrophysics and cosmology scalar field dark matter is a classical, minimally coupled, scalar field postulated to account for the inferred dark matter.

The Bolshoi simulation, a computer model of the universe run in 2010 on the Pleiades supercomputer at the NASA Ames Research Center, was the most accurate cosmological simulation to that date of the evolution of the large-scale structure of the universe. The Bolshoi simulation used the now-standard ΛCDM (Lambda-CDM) model of the universe and the WMAP five-year and seven-year cosmological parameters from NASA's Wilkinson Microwave Anisotropy Probe team. "The principal purpose of the Bolshoi simulation is to compute and model the evolution of dark matter halos, thereby rendering the invisible visible for astronomers to study, and to predict visible structure that astronomers can seek to observe." “Bolshoi” is a Russian word meaning “big.”

<span class="mw-page-title-main">Ben Moore (astrophysicist)</span> American professor of astrophysics

Ben Moore is an English professor of astrophysics, author, musician, and director of the Center for Theoretical Astrophysics and Cosmology at the University of Zürich. His research is focussed on cosmology, gravity, astroparticle physics, and planet formation. He has authored in excess of 200 scientific papers on the origin of planets and galaxies, as well as dark matter and dark energy. In his research, he simulates the universe using custom-built supercomputers.

References

  1. ↑ Peebles, P. J. E. (December 1982). "Large-scale background temperature and mass fluctuations due to scale-invariant primeval perturbations". The Astrophysical Journal. 263: L1. Bibcode:1982ApJ...263L...1P. doi: 10.1086/183911 .
  2. ↑ Bond, J. R.; Szalay, A. S.; Turner, M. S. (1982). "Formation of galaxies in a gravitino-dominated universe". Physical Review Letters. 48 (23): 1636–1639. Bibcode:1982PhRvL..48.1636B. doi:10.1103/PhysRevLett.48.1636.
  3. ↑ Blumenthal, George R.; Pagels, Heinz; Primack, Joel R. (2 September 1982). "Galaxy formation by dissipationless particles heavier than neutrinos". Nature. 299 (5878): 37–38. Bibcode:1982Natur.299...37B. doi:10.1038/299037a0. S2CID   4351645.
  4. ↑ Blumenthal, G. R.; Faber, S. M.; Primack, J. R.; Rees, M. J. (1984). "Formation of galaxies and large-scale structure with cold dark matter". Nature. 311 (517): 517–525. Bibcode:1984Natur.311..517B. doi:10.1038/311517a0. OSTI   1447148. S2CID   4324282.
  5. ↑ Battinelli, P.; S. Demers (2005-10-06). "The C star population of DDO 190: 1. Introduction". Astronomy and Astrophysics. 447 (2). Astronomy & Astrophysics: 473. Bibcode:2006A&A...447..473B. doi: 10.1051/0004-6361:20052829 . Archived from the original on 2012-08-15. Retrieved 2012-08-19. Dwarf galaxies play a crucial role in the CDM scenario for galaxy formation, having been suggested to be the natural building blocks from which larger structures are built up by merging processes. In this scenario dwarf galaxies are formed from small-scale density fluctuations in the primeval universe.{{cite journal}}: CS1 maint: bot: original URL status unknown (link)
  6. ↑ Turner, M.; et al. (2010). "Axions 2010 Workshop". Gainesville, USA: U. Florida.[ full citation needed ]
  7. ↑ Sikivie, Pierre; et al. (2008). "Axion Cosmology". Lect. Notes Phys. Vol. 741. pp. 19–50.[ full citation needed ]
  8. 1 2 Francesca Chadha-Day; John Ellis; David J. E. Marsh (23 February 2022). "Axion dark matter: What is it and why now?". Science Advances. 8 (8): eabj3618. arXiv: 2105.01406 . Bibcode:2022SciA....8J3618C. doi:10.1126/sciadv.abj3618. PMC   8865781 . PMID   35196098.
  9. ↑ Carr, B.J.; et al. (May 2010). "New cosmological constraints on primordial black holes". Physical Review D. 81 (10): 104019. arXiv: 0912.5297 . Bibcode:2010PhRvD..81j4019C. doi:10.1103/PhysRevD.81.104019. S2CID   118946242.
  10. 1 2 Peter, A.H.G. (2012). "Dark matter: A brief review". arXiv: 1201.3942 [astro-ph.CO].
  11. ↑ Bertone, Gianfranco; Hooper, Dan; Silk, Joseph (January 2005). "Particle dark matter: evidence, candidates and constraints". Physics Reports. 405 (5–6): 279–390. arXiv: hep-ph/0404175 . Bibcode:2005PhR...405..279B. doi:10.1016/j.physrep.2004.08.031. S2CID   118979310.
  12. 1 2 Garrett, Katherine; Dūda, Gintaras (2011). "Dark Matter: A Primer". Advances in Astronomy. 2011: 968283. arXiv: 1006.2483 . Bibcode:2011AdAst2011E...8G. doi: 10.1155/2011/968283 . S2CID   119180701. MACHOs can only account for a very small percentage of the nonluminous mass in our galaxy, revealing that most dark matter cannot be strongly concentrated or exist in the form of baryonic astrophysical objects. Although microlensing surveys rule out baryonic objects like brown dwarfs, black holes, and neutron stars in our galactic halo, can other forms of baryonic matter make up the bulk of dark matter? The answer, surprisingly, is no ...
  13. ↑ Bertone, Gianfranco (18 November 2010). "The moment of truth for WIMP dark matter" (PDF). Nature. 468 (7322): 389–393. doi:10.1038/nature09509. PMID   21085174. S2CID   4415912.
  14. 1 2 Olive, Keith A. (2003). "TASI lectures on dark matter". Physics. 54: 21. arXiv: astro-ph/0301505 . Bibcode:2003astro.ph..1505O.
  15. ↑ Kroupa, P.; Famaey, B.; de Boer, Klaas S.; Dabringhausen, Joerg; Pawlowski, Marcel; Boily, Christian; Jerjen, Helmut; Forbes, Duncan; Hensler, Gerhard (2010). "Local-Group tests of dark-matter Concordance Cosmology: Towards a new paradigm for structure formation". Astronomy and Astrophysics. 523: 32–54. arXiv: 1006.1647 . Bibcode:2010A&A...523A..32K. doi:10.1051/0004-6361/201014892. S2CID   11711780.
  16. ↑ Gentile, G.; Salucci, P. (2004). "The cored distribution of dark matter in spiral galaxies". Monthly Notices of the Royal Astronomical Society. 351 (3): 903–922. arXiv: astro-ph/0403154 . Bibcode:2004MNRAS.351..903G. doi:10.1111/j.1365-2966.2004.07836.x. S2CID   14308775.
  17. ↑ Klypin, Anatoly; Kravtsov, Andrey V.; Valenzuela, Octavio; Prada, Francisco (1999). "Where are the missing galactic satellites?". Astrophysical Journal. 522 (1): 82–92. arXiv: astro-ph/9901240 . Bibcode:1999ApJ...522...82K. doi:10.1086/307643. S2CID   12983798.
  18. ↑ Pawlowski, Marcel; et al. (2014). "Co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies". Monthly Notices of the Royal Astronomical Society. 442 (3): 2362–2380. arXiv: 1406.1799 . Bibcode:2014MNRAS.442.2362P. doi:10.1093/mnras/stu1005.
  19. ↑ Banik, Indranil; Zhao, H (2018-01-21). "A plane of high velocity galaxies across the Local Group". Monthly Notices of the Royal Astronomical Society. 473 (3): 4033–4054. arXiv: 1701.06559 . Bibcode:2018MNRAS.473.4033B. doi: 10.1093/mnras/stx2596 . ISSN   0035-8711.
  20. ↑ Banik, Indranil; Haslbauer, Moritz; Pawlowski, Marcel S.; Famaey, Benoit; Kroupa, Pavel (2021-06-21). "On the absence of backsplash analogues to NGC 3109 in the ΛCDM framework". Monthly Notices of the Royal Astronomical Society. 503 (4): 6170–6186. arXiv: 2105.04575 . Bibcode:2021MNRAS.503.6170B. doi: 10.1093/mnras/stab751 . ISSN   0035-8711.
  21. ↑ Kormendy, J.; Drory, N.; Bender, R.; Cornell, M.E. (2010). "Bulgeless giant galaxies challenge our picture of galaxy formation by hierarchical clustering". The Astrophysical Journal . 723 (1): 54–80. arXiv: 1009.3015 . Bibcode:2010ApJ...723...54K. doi:10.1088/0004-637X/723/1/54. S2CID   119303368.
  22. ↑ Haslbauer, M; Banik, I; Kroupa, P; Wittenburg, N; Javanmardi, B (2022-02-01). "The High Fraction of Thin Disk Galaxies Continues to Challenge ΛCDM Cosmology". The Astrophysical Journal . 925 (2): 183. arXiv: 2202.01221 . Bibcode:2022ApJ...925..183H. doi: 10.3847/1538-4357/ac46ac . ISSN   1538-4357.
  23. ↑ Sachdeva, S.; Saha, K. (2016). "Survival of pure disk galaxies over the last 8 billion years". The Astrophysical Journal Letters. 820 (1): L4. arXiv: 1602.08942 . Bibcode:2016ApJ...820L...4S. doi: 10.3847/2041-8205/820/1/L4 . S2CID   14644377.
  24. ↑ Mahmood, R; Ghafourian, N; Kashfi, T; Banik, I; Haslbauer, M; Cuomo, V; Famaey, B; Kroupa, P (2021-11-01). "Fast galaxy bars continue to challenge standard cosmology". Monthly Notices of the Royal Astronomical Society. 508 (1): 926–939. arXiv: 2106.10304 . Bibcode:2021MNRAS.508..926R. doi:10.1093/mnras/stab2553. hdl:10023/24680. ISSN   0035-8711.
  25. ↑ Rini, Matteo (2017). "Synopsis: Tackling the Small-Scale Crisis". Physical Review D. 95 (12): 121302. arXiv: 1703.10559 . Bibcode:2017PhRvD..95l1302N. doi:10.1103/PhysRevD.95.121302. S2CID   54675159.
  26. ↑ Cesari, Thaddeus (9 December 2022). "NASA's Webb Reaches New Milestone in Quest for Distant Galaxies" . Retrieved 9 December 2022.
  27. ↑ Curtis-Lake, Emma; et al. (27 February 2023). "Spectroscopic confirmation of four metal-poor galaxies at z=10.3-13.2". arXiv: 2212.04568 [astro-ph.GA].
  28. ↑ O'Callaghan, Jonathan (6 December 2022). "Astronomers Grapple with JWST's Discovery of Early Galaxies". Scientific American . Retrieved 10 December 2022.
  29. ↑ Behroozi, Peter; Conroy, Charlie; Wechsler, Risa H.; Hearin, Andrew; Williams, Christina C.; Moster, Benjamin P.; Yung, L. Y. Aaron; Somerville, Rachel S.; Gottlöber, Stefan; Yepes, Gustavo; Endsley, Ryan (December 2020). "The Universe at z > 10: predictions for JWST from the UNIVERSEMACHINE DR1". Monthly Notices of the Royal Astronomical Society. 499 (4): 5702–5718. arXiv: 2007.04988 . Bibcode:2020MNRAS.499.5702B. doi:10.1093/mnras/staa3164.
  30. ↑ Volker Springel; Lars Hernquist (February 2003). "The history of star formation in a Λ cold dark matter universe". Monthly Notices of the Royal Astronomical Society. 339 (2): 312–334. arXiv: astro-ph/0206395 . Bibcode:2003MNRAS.339..312S. doi:10.1046/j.1365-8711.2003.06207.x. S2CID   8715136.
  31. ↑ Boylan-Kolchin, Michael (2023). "Stress testing ΛCDM with high-redshift galaxy candidates". Nature Astronomy. 7 (6): 731–735. arXiv: 2208.01611 . doi:10.1038/s41550-023-01937-7. PMC   10281863 . PMID   37351007. S2CID   251252960.

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.