astro.wikisort.org - ScienceA dark galaxy is a hypothesized galaxy with no, or very few, stars. They received their name because they have no visible stars,[1] but may be detectable if they contain significant amounts of gas. Astronomers have long theorized the existence of dark galaxies, but there are no confirmed examples to date.[2] Dark galaxies are distinct from intergalactic gas clouds caused by galactic tidal interactions, since these gas clouds do not contain dark matter, so they do not technically qualify as galaxies. Distinguishing between intergalactic gas clouds and galaxies is difficult; most candidate dark galaxies turn out to be tidal gas clouds.[3] The best candidate dark galaxies to date include HI1225+01,[4] AGC229385,[5] and numerous gas clouds detected in studies of quasars.
A hypothesized galaxy with no, or very few, stars
On 25 August 2016, astronomers reported that Dragonfly 44, an ultra diffuse galaxy (UDG) with the mass of the Milky Way galaxy, but with nearly no discernable stars or galactic structure, is made almost entirely of dark matter.[6][7][8]
Observational evidence
Large surveys with sensitive, but low resolution radio telescopes like Arecibo or the Parkes Telescope look for 21 cm emission from atomic hydrogen in galaxies. These surveys are then matched to optical surveys to identify any objects with no optical counterpart, i.e. sources with no stars.
Another way astronomers search for dark galaxies is to look for hydrogen absorption lines in the spectra of background quasars. This technique has revealed many intergalactic clouds of hydrogen, but following up candidate dark galaxies is difficult, since these sources tend to be too far away, and are often optically drowned out by the bright light from the quasar.
Nature of dark galaxies
Origin
In 2005, astronomers found gas cloud VIRGOHI21 and attempted to determine what it was and why it caused such a gravitational pull on galaxy NGC 4254. After years of running out of other explanations, some have concluded that VIRGOHI21 is a dark galaxy, due to the massive effect it had on NGC 4254.[9]
Size
The actual size of dark galaxies is unknown because they cannot be observed with normal telescopes. There have been various estimations, ranging from double the size of the Milky Way[10] to the size of a small quasar.
Structure
Dark galaxies are composed of dark matter. Furthermore, dark galaxies are theoretically composed of hydrogen and dust.[9] Some scientists support the idea that dark galaxies may contain stars.[11] Yet the exact composition of dark galaxies is unknown because there is no conclusive way to spot them so far. However, astronomers estimate that the mass of the gas in these galaxies is approximately 1 billion times that of the Sun.[12]
Methodology to observe dark bodies
Dark galaxies contain no visible stars, and are not visible using optical telescopes. The Arecibo Galaxy Environment Survey (AGES) is a current study using the Arecibo radio telescope to search for dark galaxies, which are predicted to contain detectable amounts of neutral hydrogen. The Arecibo radio telescope is useful where others are not because of its ability to detect the emission from this neutral hydrogen, specifically the 21 cm line.[13] Unfortunately, the decommissioning and subsequent catastrophic collapse of the Arecibo Radio Telescope on December 1st, 2020 has somewhat limited its efficacy in facilitating further data collection.
Alternative theories
Scientists say that the galaxies we see today only began to create stars after dark galaxies. Based on numerous scientific assertions, dark galaxies played a big role in many of the galaxies astronomers and scientists see today. Martin Haehnel, from Kavli Institute for Cosmology at the University of Cambridge, claims that the precursor to the Milky Way galaxy was actually a much smaller bright galaxy that had merged with dark galaxies nearby to form the Milky Way we currently see. Multiple scientists agree that dark galaxies are building blocks of modern galaxies. Sebastian Cantalupo of the University of California, Santa Cruz, agrees with this theory. He goes on to say, "In our current theory of galaxy formation, we believe that big galaxies form from the merger of smaller galaxies. Dark galaxies bring to big galaxies a lot of gas, which then accelerates star formation in the bigger galaxies." Scientists have specific techniques they use to locate these dark galaxies. These techniques have the capability of teaching us more about other special events that occur in the universe; for instance, the “cosmic web”. This “web” is made of invisible filaments of gas and dark matter believed to permeate the universe, as well as “feeding and building galaxies and galaxy clusters where the filaments intersect.”[12]
Potential dark galaxies
HE0450-2958
Main article: HE0450-2958
HE0450-2958 is a quasar at redshift z=0.285. Hubble Space Telescope images showed that the quasar is located at the edge of a large cloud of gas, but no host galaxy was detected for the quasar. The authors of the Hubble study suggested that one possible scenario was that the quasar is located in a dark galaxy.[14] However, subsequent analysis by other groups found no evidence that the host galaxy is anomalously dark, and demonstrated that a normal host galaxy is probably present,[15][16] so the observations do not support the dark galaxy interpretation.
HVC 127-41-330
HVC 127-41-330 is a cloud rotating at high speed between Andromeda and the Triangulum Galaxy. Astronomer Josh Simon considers this cloud to be a dark galaxy because of the speed of its rotation and its predicted mass.[17][18]
Smith's Cloud
Main article: Smith's Cloud
Smith's Cloud is a candidate to be a dark galaxy, due to its projected mass and survival of encounters with the Milky Way.[19]
VIRGOHI21
Initially discovered in 2000, VIRGOHI21 was announced in February 2005 as a good candidate to be a true dark galaxy.[11][20][21][22] It was detected in 21-cm surveys, and was suspected to be a possible cosmic partner to the galaxy NGC 4254. This unusual-looking galaxy appears to be one partner in a cosmic collision, and appeared to show dynamics consistent with a dark galaxy (and apparently inconsistent with the predictions of the Modified Newtonian Dynamics (MOND) theory).[23] However, further observations revealed that VIRGOHI21 was an intergalactic gas cloud, stripped from NGC4254 by a high speed collision.[24][25][26] The high speed interaction was caused by infall into the Virgo cluster.
See also
- Dark matter – Hypothetical form of matter
- Dark matter halo – Theoretical cosmological structure
- Dwarf spheroidal galaxy – Small, low-luminosity galaxy with an old stellar population and little dust
- Low-surface-brightness galaxy
- Ultra diffuse galaxy – Extremely low luminosity galaxy
- Galaxy X (galaxy) – Dark satellite dwarf galaxy of the Milky Way Galaxy
References
- "First evidence of dark galaxies from the early Universe spotted". Zmescience.com. 2012-07-11. Retrieved 2012-08-13.
- Cannon, John M.; Martinkus, Charlotte P.; Leisman, Lukas; Haynes, Martha P.; Adams, Elizabeth A. K.; Giovanelli, Riccardo; Hallenbeck, Gregory; Janowiecki, Steven; Jones, Michael (2015-02-01). "The Alfalfa "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-To-Light Ratio Systems". The Astronomical Journal. 149 (2): 72. arXiv:1412.3018. Bibcode:2015AJ....149...72C. doi:10.1088/0004-6256/149/2/72. ISSN 0004-6256. S2CID 118592858.
- Oosterloo, T. A.; Heald, G. H.; De Blok, W. J. G. (2013). "Is GBT 1355+5439 a dark galaxy?". Astronomy & Astrophysics. 555: L7. arXiv:1306.6148. Bibcode:2013A&A...555L...7O. doi:10.1051/0004-6361/201321965. S2CID 118402005.
- "The Arecibo Legacy Fast ALFA Survey". egg.astro.cornell.edu. Retrieved 2015-09-29.
- Janowiecki, Steven; Leisman, Lukas; Józsa, Gyula; Salzer, John J.; Haynes, Martha P.; Giovanelli, Riccardo; Rhode, Katherine L.; Cannon, John M.; Adams, Elizabeth A. K. (2015-03-01). "(Almost) Dark HI Sources in the ALFALFA Survey: The Intriguing Case of HI1232+20". The Astrophysical Journal. 801 (2): 96. arXiv:1502.01296. Bibcode:2015ApJ...801...96J. doi:10.1088/0004-637X/801/2/96. ISSN 0004-637X. S2CID 119271121.
- Van Dokkum, Pieter; et al. (25 August 2016). "A High Stellar Velocity Dispersion and ~100 Globular Clusters For The Ultra-Diffuse Galaxy Dragonfly 44". The Astrophysical Journal Letters. 828 (1): L6. arXiv:1606.06291. Bibcode:2016ApJ...828L...6V. doi:10.3847/2041-8205/828/1/L6. S2CID 1275440.
- Hall, Shannon (25 August 2016). "Ghost galaxy is 99.99 per cent dark matter with almost no stars". New Scientist. Retrieved 27 August 2016.
- Feltman, Rachael (26 August 2016). "A new class of galaxy has been discovered, one made almost entirely of dark matter". The Washington Post. Retrieved 26 August 2016.
- Fraser Cain (2007-06-14). "No Stars Shine in This Dark Galaxy". Universetoday.com. Retrieved 2012-08-13.
- "Arecibo Survey Produces Dark Galaxy Candidate". Spacedaily.com. 2006-04-07. Retrieved 2012-08-13.
- Stuart Clark. "Dark galaxy' continues to puzzle astronomers". New Scientist. Retrieved 2008-02-26.
- "First Direct Detection Sheds Light On Dark Galaxies". Zmescience.com. Retrieved 22 December 2012.
- in Astronomy (2009-12-23). "Invisible Dark-Matter Galaxy has Ten Billion Xs the Mass of the Sun". Dailygalaxy.com. Archived from the original on 2018-01-04. Retrieved 2012-08-13.
- Magain P.; et al. (2005). "Discovery of a bright quasar without a massive host galaxy". Nature. 437 (7057): 381–4. arXiv:astro-ph/0509433. Bibcode:2005Natur.437..381M. doi:10.1038/nature04013. PMID 16163349. S2CID 4303895.
- Merritt, David; et al. (2006). "The nature of the HE0450-2958 system". Monthly Notices of the Royal Astronomical Society. 367 (4): 1746–1750. arXiv:astro-ph/0511315. Bibcode:2006MNRAS.367.1746M. doi:10.1111/j.1365-2966.2006.10093.x. S2CID 55834970.
- Kim, Minjin; Ho, Luis; Peng, Chien; Im, Myungshin (2007). "The Host Galaxy of the Quasar HE 0450-2958". The Astrophysical Journal. 658 (1): 107–113. arXiv:astro-ph/0611411. Bibcode:2007ApJ...658..107K. doi:10.1086/510846. S2CID 14375599.
- Josh Simon (2005). "Dark Matter in Dwarf Galaxies: Observational Tests of the Cold Dark Matter Paradigm on Small Scales" (PDF): 4273. Bibcode:2005PhDT.........2S. Archived from the original (PDF) on 2006-09-13.
- Battersby, Stephen (2003-10-20). "Astronomers find first 'dark galaxy'". New Scientist. Retrieved December 22, 2012.
- "Dark galaxy crashing into the Milky Way". New Scientist. No. 2735. 22 November 2009. Retrieved 2009-12-12.
- Clark, Stuart (2005-02-23). "Astronomers claim first 'dark galaxy' find". NewScientist.com news service. Retrieved 2006-10-26.
- Shiga, David (2005-02-26). "Ghostly Galaxy: Massive, dark cloud intrigues scientists". Science News Online. 167 (9): 131. doi:10.2307/4015891. JSTOR 4015891. Archived from the original on 2011-05-24. Retrieved 2008-09-14.
- Britt, Roy (2005-02-23). "First Invisible Galaxy Discovered in Cosmology Breakthrough". Space.com.
- Funkhouser, Scott (2005). "Testing MOND with VirgoHI21". Monthly Notices of the Royal Astronomical Society. 364 (1): 237. arXiv:astro-ph/0503104. Bibcode:2005MNRAS.364..237F. doi:10.1111/j.1365-2966.2005.09565.x. S2CID 119368923.
- Kent, Brian R.; Giovanelli, Riccardo; Haynes, Martha P.; Saintonge, Amélie; Stierwalt, Sabrina; Balonek, Thomas; Brosch, Noah; Catinella, Barbara; Koopmann, Rebecca A. (2007-08-01). "Optically Unseen H I Detections toward the Virgo Cluster Detected in the Arecibo Legacy Fast ALFA Survey". The Astrophysical Journal Letters. 665 (1): L15–L18. Bibcode:2007ApJ...665L..15K. doi:10.1086/521100. ISSN 0004-637X.
- Duc, Pierre-Alain; Bournaud, Frederic (2008-02-01). "Tidal Debris from High-Velocity Collisions as Fake Dark Galaxies: A Numerical Model of VIRGOHI 21". The Astrophysical Journal. 673 (2): 787–797. arXiv:0710.3867. Bibcode:2008ApJ...673..787D. doi:10.1086/524868. ISSN 0004-637X. S2CID 15348867.
- Haynes, Martha P.; Giovanelli, Riccardo; Kent, Brian R. (2007). "NGC 4254: An Act of Harassment Uncovered by the Arecibo Legacy Fast ALFA Survey". Astrophysical Journal. 665 (1): L19–22. arXiv:0707.0113. Bibcode:2007ApJ...665L..19H. doi:10.1086/521188. S2CID 12930657.
External links
Galaxies |
---|
Morphology | |
---|
Structure |
- Active galactic nucleus
- Bar
- Bulge
- Central massive object
- Dark matter halo
- Disc
- Halo
- Galactic plane
- Galactic ridge
- Interstellar medium
- Protogalaxy
- Galaxy filament
- Spiral arm
- Supermassive black hole
|
---|
Active nuclei |
- Blazar
- LINER
- Markarian
- Quasar
- BL Lacertae object
- Radio
- Relativistic jet
- Seyfert
|
---|
Energetic galaxies |
- Lyman-alpha emitter
- Lyman-break
- Luminous infrared
- Starburst
- blue compact dwarf
- pea
- faint blue
- Luminous infrared galaxy
- Hot dust-obscured
- Green bean galaxy
- Hanny's Voorwerp
|
---|
Low activity |
- Low surface brightness
- Ultra diffuse
- Dark galaxy
- Red nugget
|
---|
Interaction |
- Field
- Galactic tide
- Groups and clusters
- group
- cluster
- Brightest cluster galaxy
- fossil group
- Interacting
- merger
- collision
- cannibalism
- Jellyfish
- Satellite
- Stellar stream
- Superclusters
- Walls
- Voids and supervoids
|
---|
Lists |
- Galaxies
- Galaxies named after people
- Largest
- Nearest
- Polar-ring
- Ring
- Spiral
- Groups and clusters
- Large quasar groups
- Quasars
- List of the most distant astronomical objects
- Starburst galaxies
- Superclusters
- Voids
|
---|
See also |
- Extragalactic astronomy
- Galactic astronomy
- Galactic coordinate system
- Galactic empire
- Galactic habitable zone
- Galactic magnetic fields
- Galactic orientation
- Galactic quadrant
- Galaxy color–magnitude diagram
- Galaxy formation and evolution
- Galaxy rotation curve
- Gravitational lens
- Gravitational microlensing
- Illustris project
- Intergalactic dust
- Intergalactic stars
- Intergalactic travel
- Population III stars
|
---|
Category
Portal
|
|
---|
Forms of dark matter | | |
---|
Hypothetical particles |
- Axino
- Axion
- Dark photon
- LSP
- Minicharged particle
- Neutralino
- Sterile neutrino
- SIMP
- WIMP
- WISP
|
---|
Theories and objects | |
---|
Search experiments | Direct detection |
- ADMX
- ANAIS
- ArDM
- CDEX
- CDMS
- CLEAN
- CoGeNT
- COSINE
- COUPP
- CRESST
- CUORE
- D3
- DAMA/LIBRA
- DAMA/NaI
- DAMIC
- DarkSide
- DARWIN
- DEAP
- DM-Ice
- DMTPC
- DRIFT
- EDELWEISS
- EURECA
- KIMS
- LUX
- LZ
- MACRO
- MIMAC
- NAIAD
- NEWAGE
- NEWS-G
- PandaX
- PICASSO
- PICO
- ROSEBUD
- SABRE
- SIMPLE
- TREX-DM
- UKDMC
- WARP
- XENON
- XMASS
- ZEPLIN
|
---|
Indirect detection | |
---|
Other projects | |
---|
|
---|
Potential dark galaxies | |
---|
Related | |
---|
|
На других языках
[de] Dunkle Galaxie
Eine Dunkle Galaxie ist eine Galaxie, deren Masse zu einem Großteil aus nicht selbstleuchtender Materie besteht und somit nur sehr wenige bis gar keine Sterne enthält. Daher auch der Namenszusatz „Dunkel“.
- [en] Dark galaxy
[ru] Тёмная галактика
Тёмная галактика — гипотетический объект галактических размеров, который содержит очень мало или вовсе не содержит звёзд (отсюда и «тёмная»), удерживаемых вместе тёмной материей. Она может также содержать газ и пыль. Хотя есть некоторые потенциальные кандидаты, существование тёмных галактик на сегодняшний день не подтверждено.
Текст в блоке "Читать" взят с сайта "Википедия" и доступен по лицензии Creative Commons Attribution-ShareAlike; в отдельных случаях могут действовать дополнительные условия.
Другой контент может иметь иную лицензию. Перед использованием материалов сайта WikiSort.org внимательно изучите правила лицензирования конкретных элементов наполнения сайта.
2019-2025
WikiSort.org - проект по пересортировке и дополнению контента Википедии