NGC 5824 in the Hubble Space Telescope Mapping
Italian scientists examined the chemical composition of the massive globular clusters of NGC 5824 living in the Milky Way. New analysis provides some hints on the nature of the cluster.
NGC 5824 is 105,000 light-years distant and lives on the territory of the Wolf. Before us is a large representative of the ball type in the outer halo of our galaxy. The chemical composition for many years caused many questions.
In May 2015, he was followed up with a FLAMES spectrograph on the Very Large Telescope (Chile). Then it was possible to obtain high-resolution spectra of 117 giants. The collected data allowed to obtain information about the chemical filling of stars.
Early studies have shown that NGC 5824 has an internal distribution of iron content. However, the new analysis did not confirm this assumption. It turned out that the cluster is endowed with an average iron index of 2.14 and does not show signs of its own distribution. Therefore, the new classification defines it as a normal globular cluster. We also managed to find traces of chemical anomalies, such as sodium-oxygen (Na-O) and magnesium-aluminum (Mg-Al) anti-correlations characteristic of the ball type. A huge range of the ratio of magnesium and iron is observed, which is observed only in a few metal-poor and massive clusters. Perhaps this is a process of effective self-enrichment, due to the massive asymptotic stars of giant branches.
