Volume 490, Number 1, October IV 2008
|Page(s)||97 - 101|
|Published online||11 September 2008|
The magnitue-diameter relation in galaxies
National Research Council of Canada, Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, 5071 W. Saanich Rd., Victoria, BC, V9E 2E7, Canada
Accepted: 21 August 2008
Aims. We investigate the dependence of the luminosity-diameter relation of galaxies on the environment.
Methods. This study is based on a comparison between the 80 galaxies in the Shapley-Ames Catalog that are located within a distance of 10 Mpc, and the luminosity-diameter relation for galaxies in great clusters such as Virgo and Coma.
Results. A relatively tight linear correlation is observed between the absolute magnitudes and the logarithms of the linear diameters of galaxies located within 10 Mpc. Surprisingly this observed power-law relationship appears to be almost independent of environment and local mass density as defined by Karachentsev & Malakov. However, at a given luminosity, early-type galaxies are (on average) slightly more compact than are objects of a later type. Unexpectedly the present results appear to indicate that the luminosity-diameter relation for the galaxies within 10 Mpc is indistinguishable from what is observed in the much denser Virgo cluster.
Conclusions. Galaxies appear to form an almost one-dimensional family in parameter space. It remains a mystery why the luminosity-diameter relation for galaxies is so insensitive to environment.
Key words: galaxies: luminosity function, mass function
© ESO, 2008
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