Solar abundance ratios of the iron-peak elements in the Perseus cluster

High-resolution X-ray spectra show near-solar abundances of chromium, manganese and nickel with respect to iron in the Perseus cluster, suggesting that the progenitors of type Ia supernovae could be near- and sub-Chandrasekhar-mass white dwarfs. Solar abundances in the Perseus cluster Clusters of galaxies are embedded in hot gas, the elemental abundances of which arise from the cumulative effects of all of the supernovae that have occurred in the galaxies over the life of the cluster. Recent work found that these abundances were different from the solar ones, suggesting that the history of supernovae in the clusters diverged from what is seen in the Milky Way. However, limitations of the instruments made these observations difficult. Hiroya Yamaguchi and the rest of the Hitomi Collaboration now report very high-spectral-resolution observations of the Perseus cluster that reveal near-solar abundance ratios of elements near the iron peak. They conclude that a mixture of near- and sub-Chandrasekhar-mass white dwarfs contributed those elements through type Ia supernova explosions. The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae 1 . Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode 2 , 3 , 4 , 5 , 6 . Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun 7 , 8 , 9 , 10 , 11 , suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, high-resolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and