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In cosmology, galaxy filaments (subtypes: supercluster complexes, galaxy walls, and galaxy sheets) are the largest known structures in the universe, consisting of walls of gravitationally bound galaxy superclusters. These massive, thread-like formations can reach 80 megaparsecs h−1 (or of the order of 160 to 260 million light-years) and form the boundaries between large voids.
In the standard model of the evolution of the universe, galactic filaments form along and follow web-like strings of dark matter. It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts baryonic matter, and it is this "normal" matter that astronomers see forming long, thin walls of super-galactic clusters.
Discovery of structures larger than superclusters began in the late-1980s. In 1987, astronomer R. Brent Tully of the University of Hawaii's Institute of Astronomy identified what he called the Pisces–Cetus Supercluster Complex. In 1989, the CfA2 Great Wall was discovered, followed by the Sloan Great Wall in 2003. On January 11, 2013, researchers led by Roger Clowes of the University of Central Lancashire announced the discovery of a large quasar group, the Huge-LQG, which dwarfs previously discovered galaxy filaments in size. In November 2013, using gamma-ray bursts as reference points, astronomers discovered the Hercules–Corona Borealis Great Wall, an extremely huge filament measuring more than 10 billion light-years across.
Filament subtype of filaments have roughly similar major and minor axes in cross-section, along the lengthwise axis.
|Coma Filament||The Coma Supercluster lies within the Coma Filament. It forms part of the CfA2 Great Wall.|
|Perseus–Pegasus Filament||1985||Connected to the Pisces–Cetus Supercluster, with the Perseus–Pisces Supercluster being a member of the filament.|
|Ursa Major Filament||Connected to the CfA Homunculus, a portion of the filament forms a portion of the "leg" of the Homunculus.|
|Lynx–Ursa Major Filament (LUM Filament)||1999||from 2000 km/s to 8000 km/s in redshift space||Connected to and separate from the Lynx–Ursa Major Supercluster.|
|z=2.38 filament around protocluster ClG J2143-4423||2004||z=2.38||110Mpc||A filament the length of the Great Wall was discovered in 2004. As of 2008, it was still the largest structure beyond redshift 2.|
The galaxy wall subtype of filaments have a significantly greater major axis than minor axis in cross-section, along the lengthwise axis.
|CfA2 Great Wall (Coma Wall, Great Wall, Northern Great Wall, Great Northern Wall, CfA Great Wall)||1989||z=0.03058||251Mpc long
||This was the first super-large large-scale structure or pseudo-structure in the universe to be discovered. The CfA Homunculus lies at the heart of the Great Wall, and the Coma Supercluster forms most of the homunculus structure. The Coma Cluster lies at the core.|
|Sloan Great Wall (SDSS Great Wall)||2003||z=0.07804||433Mpc long||This was the largest known galaxy filament to be discovered, until it was eclipsed by the Hercules–Corona Borealis Great Wall found ten years later.|
|Sculptor Wall (Southern Great Wall, Great Southern Wall, Southern Wall)||8000 km/s long
5000 km/s wide
1000 km/s deep
(in redshift space dimensions)
|The Sculptor Wall is "parallel" to the Fornax Wall and "perpendicular" to the Grus Wall.|
|Grus Wall||The Grus Wall is "perpendicular" to the Fornax and Sculptor Walls.|
|Fornax Wall||The Fornax Cluster is part of this wall. The wall is "parallel" to the Sculptor Wall and "perpendicular" to the Grus Wall.|
|Hercules–Corona Borealis Great Wall||2013||z≈2||3 Gpc long,
150 000 km/s deep
(in redshift space)
|The largest known structure in the universe. This is also the first time since 1991 that a galaxy filament/great wall held the record as the largest known structure in the universe.|
||It was the largest known structure in the universe from 1991 to 2011, until U1.11's discovery.|
||Was the largest known structure in the universe for a few months, until Huge-LQG's discovery.|
||It was the largest structure known in the universe, until the discovery of the Hercules–Corona Borealis Great Wall found one year later.|
|Pisces–Cetus Supercluster Complex||1987||1 billion ly wide,
150 million ly deep
|Contains Virgo Supercluster and Local Group|
The universe within 1 billion light-years (307 Mpc) of Earth, showing local superclusters forming filaments and voids
Map of nearest walls, voids and superclusters
2dF survey map, containing the SDSS Great Wall
2MASS XSC infrared sky map