We have investigated the baryon-mass content in a subsample of 19 clusters of galaxies extracted from the X-ray flux-limited sample HIFLUGCS according to their positions in the sky .
For these clusters , we measured total masses and characteristic radii on the basis of a rich optical spectroscopic data set , the physical properties of the intracluster medium ( ICM ) using XMM-Newton and ROSAT X-ray data , and total ( galaxy ) stellar masses utilizing the SDSS DR7 multi-band imaging .
The observed ( hot ) gas-mass fractions are almost constant in this mass range .
We confirm that the stellar mass fraction decreases as the total mass increases and shows ( 20 \pm 4 ) % scatter ; in addition , we show that it decreases as the central entropy increases .
The latter behavior supports a twofold interpretation where heating from merging quenches the star-formation activity of galaxies in massive systems , and feedback from supernovae and/or radio galaxies drives a significant amount of gas to the regions beyond r _ { 500 } or , alternatively , a substantially large amount of intracluster light ( ICL ) is associated with galaxies in nonrelaxed systems .
Furthermore , less massive clusters are confirmed to host less gas per unit total mass ; however , they exhibit higher mass fractions in metals , so that their ICM is more metal-rich .
This again supports the interpretation that in the potential wells of low-mass systems the star-formation efficiency of galaxies was high or , alternatively , some gas is missing from the hot phase of the ICM .
The former hypothesis is preferred as the main driver of the mass-dependent metal enrichment since the total mass-to-optical luminosity ratio increases as the total mass increases .
osmology : observations — Galaxies : clusters : general — Methods : data analysis — Surveys — X-rays : galaxies : clusters — Galaxies : stellar content