IRON DISTRIBUTION IN THE INTRACLUSTER GAS OF THE VIRGO CLUSTER OF GALAXIES

DIFFUSE X-ray emission, particularly fluorescence from the iron K line, from hot gas in the clusters of galaxies provides valuable information on the structure and evolution of the clusters 1. Because heavy elements such as iron are made in stars, the presence of iron distinguishes gas that originated in galaxies from primordial gas that has remained unprocessed since formation of the cluster. Previous observations of about 20 clusters indicate that iron abundance in the hot gas is about half the cosmic value 2, but these observations were made with non-imaging devices which gave no information on the spatial distribution of the iron. Lack of spatial distribution can also skew the estimated mean iron abundance determined in this way. Here we report evidence of an iron abundance gradient in hot gas in the Virgo cluster of galaxies. Iron is centrally concentrated, indicating that gas at the cluster core has been enriched by galactic mass loss.