Low Surface Brightness Galaxy
A Low Surface Brightness Galaxy (short LSB ) is a galaxy with a surface brightness, which is below the brightness of the night sky. Since the background brightness of the night sky, the airglow, depending upon, among other things, on the number of aerosols and dust particles in the air as well as the height of the observation site is a surface brightness of less than 23 mostly for the LSB may per square arcsecond elected in Johnston B system. This definition does not describe an intrinsic property, but also can depend on the angle at which a galaxy of the earth is observed. Below the Low Surface Brightness Galaxies, there is the class of Ultra Faint Dwarf Galaxies, whose surface brightness is like below 28 per square arcsecond.
Compared with High Surface Brightness (HSB ) galaxies are the Low Surface Brightness Galaxies gas-rich present with a high proportion of neutral hydrogen, the diffusely distributed. They show only a very low star formation rate and the LSBs are often isolated from other galaxies, which is why there has been no lack of gravitational interaction to a starburst. Broadly the Low Surface Brightness Galaxies divided into large spiral galaxies and elliptical or irregular dwarf galaxies. Although there are large elliptical galaxies as LSBs, but these are extremely rare. The spiral galaxies with low surface brightness partly belong to the largest known spiral galaxies. They are home in their bulges often weak active galactic nuclei.
The stars in Low Surface Brightness Galaxies are on average bluer than in HSBS and its metallicity is lower. It is concluded that the star formation in LSBs has not already been completed, but these galaxies a smaller than average rate of star formation show since its birth. LSBs follow the same Tully -Fisher relation as the HSBS.
From the rotation curves of Low Surface Brightness Galaxies follows that their mass is composed predominantly of undetectable matter and they provide a test for alternative Newtonian dynamics dar.
Share of the baryonic matter
Although there are already hundreds of low surface brightness galaxy can their share of the total baryonic matter only be roughly estimated, because we know so far no lower limit their surface brightness. Their share in the matter with a rest mass is at least 75 percent and could be as high as 97%.
- Malin 1
- UGC 6614
- Malin 2
- UGC 9024