Colour Dependence of the Distribution of IRAS Galaxies revealed by Multifractal Measures

Abstract

Multifractal measures are applied to three IRAS galaxy subsamples selected by colour from the PSCz catalogue. As shown by generalised dimension spectrum, hot IRAS galaxies are found less clustered than cold galaxies, but the difference is very weak. An alternative tool, the conditional multifractal dimension spectrum reveals apparent peculiarity of the distribution of hot galaxies, especially at high orders. The conditional multifractal measure is basically measuring the environment of selected galaxies. A detailed analysis of the distribution of galaxies with their number of neighbours turns out that cold galaxies are more likely living in over dense regions than hot galaxies. Further studies suggest that, since the colour of IRAS galaxies is a good trace of star formation rate, it is possible that we have statistical evidence here for enhanced star formation rate due to galaxy interactions

minor revision; accepted by A&A