2007ApJ...667L..41S

We studied the properties of the intracluster medium (ICM) in two clusters of galaxies (AWM 7 and Abell 1060) and two groups (HCG 62 and NGC 507) with the X-ray observatory Suzaku. Based on spatially resolved energy spectra, we measured for the first time precise cumulative ICM metal masses within 0.1 and ∼0.3r₁₈₀. Comparing our results with supernova nucleosynthesis models, the number ratio of Type II (SNe II) to Type Ia (SNe Ia) is estimated to be ∼3.5, assuming the metal mass in the ICM is represented by the sum of products synthesized in SNe Ia and SNe II. Normalized by the K-band luminosities of present galaxies, and including the metals in stars, the integrated number of past SN II explosions is estimated to be close to or somewhat higher than the star formation rate determined from Hubble Deep Field observations.