Subaru Observations for theK-Band Luminosity Distribution of Galaxies in Clusters near to 3C 324 atz∼ 1.2

We investigate the $K$-band luminosity distribution of galaxies in the regionof clusters at $z\sim1.2$ near to the radio galaxy 3C 324. The imaging datawere obtained during the commissioning period of the Subaru telescope. There isa significant excess of the surface number density of the galaxies with $K =$17--20 mag in the region within $\sim$ 40'' from 3C 324. At this bright end,the measured luminosity distribution shows a drop, which can be represented bythe exponential cut off of the Schechter-function formula; the best-fittedvalue of the characteristic magnitude, $K^{*}$, is $\sim 18.4\pm0.8$. Thismeasurement follows the evolutionary trend of the $K^*$ of the rich clustersobserved at an intermediate redshift, which is consistent with passiveevolution models with a formation redshift $z_f \gtsim 2$. At $K \gtsim 20$mag, however, the excess of the galaxy surface density in the region of theclusters decreases abruptly, which may imply that the luminosity function ofthe cluster galaxies has a negative slope at the faint end. This may implystrong luminosity segregation between the inner and outer parts of theclusters, or some deficit of faint galaxies in the cluster central region ofthe cluster.Comment: 12 pages, 9 figures, accepted for publication in PAS