A low-surface-brightness galaxy, or LSB galaxy, is a diffuse

galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar Sys ...

with a

surface brightness In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on ...

that, when viewed from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...

, is at least one magnitude lower than the ambient night sky. Most LSBs are dwarf galaxies, and most of their

baryon In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classi ...

ic matter is in the form of neutral gaseous hydrogen, rather than stars. They appear to have over 95% of their mass as non-

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

. There appears to be little supernova (SN) activity in these galaxies, although LSB galaxy IC 217 hosted 2014cl. Rotation curve measurements indicate an extremely high mass-to-light ratio, meaning that stars and luminous gas contribute only very little to the overall mass balance of an LSB. The centers of LSBs show no large overdensities in stars, unlike e.g. the bulges of normal spiral galaxies. Therefore, they seem to be dark-matter-dominated even in their centers, which makes them excellent laboratories for the study of dark matter. In comparison to the high-surface-brightness galaxies, LSBs are mainly isolated field galaxies, found in regions devoid of other galaxies. In their past, they had fewer tidal interactions or mergers with other galaxies, which could have triggered enhanced star formation. This is an explanation for the small stellar content. LSB galaxies were theorized to exist in 1976 by

Mike Disney Michael John Disney (born Bristol, England, 7 October 1937) is an astrophysicist. He discovered the optical component of the Crab Pulsar in 1969 with John Cocke. This was the first optical pulsar ever observed. He was also one of the pioneers i ...

Giant low-surface-brightness galaxies

Giant low surface brightness (GLSB) galaxies are among the most massive known spiral galaxies in the Universe. They have very faint stellar disks that are very rich in neutral hydrogen but low in

star formation Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. As a branch of astronomy, star formation includ ...

and thus low in surface brightness. Such galaxies often have bright bulges that can host low luminosity

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not prod ...

. GLSB galaxies are usually isolated systems that rarely interact with other galaxies. The first LSB galaxy verified to exist was Malin 1, discovered in 1986. As such, it was also the first giant LSB galaxy identified. At the time of its discovery, it was the largest spiral galaxy known (by scale-length measurement).Scientific American, "The Ghostliest Galaxies", GD Bothun, Vol. 276, No. 2, ''February 1997'', pp.40-45, Ken Crosswell
"Malin 1: A Bizarre Galaxy Gets Slightly Less So"
''22 January 2007''

UGC 1382 UGC may refer to: Science and technology * Universal gravitational constant G, in physics * Uppsala General Catalogue, an astronomical catalogue of galaxies * UGC, a codon for cysteine * Unique games conjecture, a conjecture in computational comp ...

was previously thought to be an elliptical galaxy, but low-brightness spiral arms were later detected. UGC 1382 is much closer to Earth than Malin 1.

Examples

* Andromeda V * Pegasus Dwarf Spheroidal Galaxy * IC 10 * NGC 45 *

Eridanus II The Eridanus II Dwarf is a low-surface brightness dwarf galaxy in the constellation Eridanus. Eridanus II was independently discovered by two groups in 2015, using data from the Dark Energy Survey ( Bechtol et al., 2015; Koposov et al. 2015 ...

* Malin 1 *

Malin 2 Malin may refer to: Places * 4766 (1987 FF1) Malin, an asteroid, see List of minor planets: 4001–5000 * Rivière du Malin (Malin River), a tributary of Jacques-Cartier River, in Quebec, Canada * Malin, Homalin, Sagaing Region, Burma * Malin ...

* Phoenix Dwarf * Sagittarius Dwarf Irregular Galaxy ( SagDIG) * Sextans A *

Sextans B Sextans B (also known as UGC 5373 and DDO 70) is an irregular galaxy that may be part of the Local Group, or lie just beyond it. Sextans B is 4.44 million light-years away from Earth and thus is one of the most distant members of the Local Gro ...

Wolf–Lundmark–Melotte The Wolf–Lundmark–Melotte (WLM) is a barred irregular galaxy discovered in 1909 by Max Wolf, located on the outer edges of the Local Group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melo ...

galaxy (WLM) *

UGC 477 UGC 477 is a low surface brightness ( LSB) galaxy, located in the Pisces constellation. It is located over 110 million light years away. At around 100,000 light years across, it is similar in size to the Milky Way galaxy A galaxy is a syst ...

References

*K. O'Neil
The HI Content and Extent of Low Surface Brightness Galaxies - Could LSB Galaxies be Responsible for Damped Ly-alpha Absorption?
For publication in ''Extragalactic Gas at Low Redshift'', by Mulchaey, et al., eds (2001). *S.D. Rosenbaum and D.J. Bomans
The environment of Low Surface Brightness Galaxies
''Astronomy & Astrophysics Letters'', 422, 5-8 (2004). *A.J. Barth
A normal stellar disk in the galaxy Malin 1
''

Astronomical Journal ''The Astronomical Journal'' (often abbreviated ''AJ'' in scientific papers and references) is a peer-reviewed monthly scientific journal owned by the American Astronomical Society (AAS) and currently published by IOP Publishing. It is one of the ...

'' 133, 1085-1091 (2007). {{Portal bar, Stars, Spaceflight, Outer space, Solar System

Giant low-surface-brightness galaxies

Examples

See also

References