Surface brightness fluctuation
The method of surface brightness fluctuation (German translation: surface brightness - fluctuation ) is a secondary method of measuring distance for galaxies and globular clusters . The method is based on the fact that in star systems the amplitude of the brightness fluctuations decreases with increasing distance , and achieves an accuracy of up to two percent for early galaxy types .
The surface brightness fluctuation is measured as the variance of the image of a galaxy, caused by the stochastic distribution of luminosity and the number of stars that fall into a resolved picture element. After subtracting the foreground and background sources, the mean brightness curve of the galaxy is subtracted and the power spectrum is calculated from the result .
The mean amplitude of the brightness fluctuations depends on the population composition of the galaxy, whereby the highest accuracy is achieved in elliptical systems without star formation .
Depending on the wavelength , different star classes carry the largest share of the emitted radiation; their distribution influences the achievable accuracy of the Surface Brightness Fluctuation method:
- in the UV the stars on the horizontal branch and the Post-AGB stars
- in the optical, mostly the red giants
- The AGB stars in the near infrared .
The Surface Brightness Fluctuation method is calibrated using primary distance measurement methods such as
- the period-luminosity relationship of Cepheids
- the Tip of the Red Giant Branch
- Type Ia supernova
- the luminosity function of planetary nebulae (Planetary Nebula Luminosity Function)
- or based on synthetic population calculations.
The accuracy could be determined by space-based observations, e.g. B. by the Hubble Space Telescope , can be increased significantly, in which the atmospheric seeing is suppressed. The method can now be used for distances between 10 and 150 mega parsec . Beyond these distances, the brightness fluctuations become too small with the resolution that can be achieved today .
- Alexander Fritz: Distance Measurements and Stellar Population Properties via Surface Brightness Fluctuations . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.1498v1 .
- John Blakeslee: Surface Brightness Fluctuations as Primary and Secondary Distance Indicators . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1202.0581v1 .
- John P. Blakeslee, Michele Cantiello, Simona Mei, Patrick Cote, Regina Barber DeGraaff, Laura Ferrarese, Andres Jordan, Eric W. Peng, John L. Tonry, Guy Worthey: Surface Brightness Fluctuations in the Hubble Space Telescope ACS / WFC F814W Bandpass and an Update on Galaxy Distances . 2010, arxiv : 1009.3270v2 .