Low surface brightness galaxy
- Low surface brightness galaxy
A low surface brightness galaxy or "LSB galaxy" is a diffuse galaxy with a surface brightness that, when viewed from Earth, is at least one magnitude lower than the ambient night sky.
Most LSBs are dwarf galaxies, in which most of their baryonic matter is still neutral gaseous hydrogen not locked up in stars. They appear to have over 95%Fact|date=July 2007 of their mass as non-baryonic dark matter. There appears to be no supernova activity in these galaxies. It is estimated that 90% of all galaxies are LSB galaxies, not high-surface-brightness types. Currently around 3000 are catalogued (as of 2005).
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 center of LSBs show no large overdensity in stars, unlike e.g. the bulge of normal spiral galaxies. Therefore they seem to be dark matter dominated even in their center which makes them an excellent laboratory to study dark matter systems.
In comparison to the more well-studied 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.
Examples
* Andromeda V
* Pegasus Dwarf Spheroidal Galaxy
* IC 10
* Phoenix Dwarf Galaxy
* Sagittarius Dwarf Irregular Galaxy (SagDIG)
* Sextans A
* Sextans B
* Wolf-Lundmark-Melotte Galaxy (WLM)
References
*K. O'Neil, [http://aps.arxiv.org/abs/astro-ph/0107064 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, [http://adsabs.harvard.edu/abs/2004A%26A...422L...5R The environment of Low Surface Brightness Galaxies] . "Astronomy & Astrophysics Letters", 422, 5-8 (2004).
*A.J. Barth, [http://lanl.arxiv.org/abs/astro-ph/0701018 A normal stellar disk in the galaxy Malin 1] . "Astronomical Journal" 133, 1085-1091 (2007).
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