Low Surface Brightness Galaxy

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A Low Surface Brightness Galaxy ( LSB for short ; literally a galaxy with low surface brightness ) is a galaxy with a surface brightness that is below the brightness of the night sky .

Since the background brightness of the night sky, the airglow , etc. a. Depending on the number of aerosols and dust particles in the air as well as the altitude of the observation point, a surface brightness of less than 23 mag per square arcsecond in the Johnson B system is usually chosen for the LSB  . This definition does not describe an intrinsic property, but can depend on the angle at which a galaxy is observed from Earth.

Below the Low Surface Brightness Galaxies there is the class of Ultra Faint Dwarf Galaxies , whose surface brightness is below 28 mag per square arc second.

properties

Compared to High Surface Brightness (HSB) galaxies, the Low Surface Brightness galaxies are richer in gas, with a high proportion of neutral hydrogen , which is diffusely distributed. They show only a very low star formation rate and are often isolated from other galaxies, which is why a starburst did not occur due to the lack of gravitational interaction .

The low surface brightness galaxies are roughly divided into large spiral galaxies and elliptical or irregular dwarf galaxies . There are also large elliptical galaxies as LSBs, but these are extremely rare. The spiral galaxies with a low surface brightness are partly among the largest known spiral galaxies. They often harbor weak active galactic nuclei in their bulges .

The stars in low surface brightness galaxies are, on average, bluer than in HSBs, and their metallicity is lower. It is concluded from this that star formation has not already ended in LSBs, but that these galaxies have shown a below-average star formation rate since their birth . LSBs follow the same Tully-Fisher relationship as the HSBs.

From the rotation curves of low surface brightness galaxies it follows that their mass mainly consists of undetectable matter or they represent a test for alternative Newtonian dynamics .

Share in baryonic matter

Although hundreds of low surface brightness galaxies are already known, their share in the total baryonic matter can only be roughly estimated because no lower limit of their surface brightness is known yet. Their proportion of matter with a mass is at least 75 percent and could be up to 97%.

Examples

literature

  • Igor D. Karachentsev, Dirk Bautzmann, Fabian Neyer, Robert Polzl, Peter Riepe, Thorsten Zilch, Bruno Mattern: Three low surface brightness dwarfs discovered around NGC 4631 . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1401.2719v1 (English).
  • James Schombert, Stacy McGaugh: Stellar Populations and the Star Formation Histories of LSB Galaxies: IV Spitzer Surface Photometry of LSB Galaxies . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1401.0238v1 (English).
  • Mousumi Das: Giant Low Surface Brightness Galaxies: Evolution in Isolation . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1310.6495v1 (English).
  • Margaret J. Geller , Antonaldo Diaferio, Michael J. Kurtz, Ian P. Dell'Antonio, Daniel G. Fabricant: The Faint End of the Luminosity Function and Low Surface Brightness Galaxies . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1107.2930v1 (English).
  • K. O'Neil: Gas, Stars and Baryons in Low Surface Brightness Galaxies . In: Astrophysics. Solar and Stellar Astrophysics . 2000, arxiv : astro-ph / 0006253v1 (English).

Individual evidence

  1. ↑ Surprise: Small elliptical galaxy actually a giant disk . July 11, 2016. Accessed October 1, 2016. UGC 1382 was initially mistaken for an ordinary elliptical galaxy until the "low-brightness" spiral arms were discovered. UGC 1382 is much closer to Earth than Malin 1.