Astron. Astrophys. 337, 31-38 (1998)
Available formats: HTML | PDF | (gzipped) PostScript Cluster luminosity function and nth ranked magnitude as a distance indicator ^{*} ^{**}
S. Rauzy ^{ 1},
C. Adami ^{ 2} and
A. Mazure ^{ 2}
Received 20 April 1998 / Accepted 4 June 1998 Abstract We define here a standard candle to determine the distance of clusters of galaxies and to investigate their peculiar velocities by using the nth rank galaxy (magnitude m_{n}). We address the question of the universality of the luminosity function for a sample of 28 rich clusters of galaxies (cz20000 km.s^{-1}) in order to model the influence on m_{n} of cluster richness. This luminosity function is found to be universal and the fit of a Schechter profile gives =-1.500.11 and in the range [-21,-17]. The uncorrected distance indicator m_{n} is more efficient for the first ranks n. With n=5, we have a dispersion of 0.61 magnitude for the (m_{n},5log(cz)) relation. When we correct for the richness effect and subtract the background galaxies we reduce the uncertainty to 0.21 magnitude with n=15. Simulations show that a large part of this dispersion originates from the intrinsic scatter of the standard candle itself. These provide upper bounds on the amplitude of cluster radial peculiar motions. At a confidence level of 90 , the dispersion is 0.13 magnitude and is limited to 1200 km.s^{-1} for our sample of clusters. Key words: cosmology: distance scale cosmology: large-scale structure of Universe galaxies: clusters galaxies: luminosity function
* Based on observations collected at the European Southern Observatory (La Silla, Chile) Send offprint requests to: C. Adami Online publication: August 6, 1998 |