We explore the near-infrared ( NIR ) K -band properties of galaxies within 93 galaxy clusters and groups using data from the Two Micron All Sky Survey ( 2MASS ) .
We use X-ray properties of these clusters to pinpoint cluster centers and estimate cluster masses .
By stacking all these systems , we study the shape of the cluster luminosity function and the galaxy distribution within the clusters .
We find that the galaxy profile is well described by the NFW profile with a concentration parameter c \sim 3 , with no evidence for cluster mass dependence of the concentration .
Using this sample , whose masses span the range from 3 \times 10 ^ { 13 } M _ { \odot } to 2 \times 10 ^ { 15 } M _ { \odot } , we confirm the existence of a tight correlation between total galaxy NIR luminosity and cluster binding mass , which indicates that NIR light can serve as a cluster mass indicator .
From the observed galaxy profile , together with cluster mass profile measurements from the literature , we find that the mass–to–light ratio is a weakly decreasing function of cluster radius , and that it increases with cluster mass .
We also derive the mean number of galaxies within halos of a given mass , the halo occupation number .
We find that the mean number scales as N \propto M ^ { 0.84 \pm 0.04 } for galaxies brighter than M _ { K } = -21 , indicating high mass clusters have fewer galaxies per unit mass than low mass clusters .
Using published observations at high redshift , we show that higher redshift clusters have higher mean occupation number than nearby systems of the same mass .
By comparing the luminosity function and radial distribution of galaxies in low mass and high mass clusters , we show that there is a marked decrease in the number density of galaxies fainter than M _ { * } as one moves to higher mass clusters ; in addition , extremely luminous galaxies are more probable in high mass clusters .
We explore several processes– including tidal interactions and merging– as a way of explaining the variation in galaxy population with cluster mass .