Scientists have measured abundance in 11 globular clusters in the galaxies NGC 147, NGC 6822 and Messier 33. The new study can expand our knowledge of the chemical composition of stellar populations in the universe.
Globular clusters are spheroidal collections of densely coupled stars orbiting galaxies. For researchers, these are valuable laboratories that allow the study of the evolution of stars and chemicals.
Therefore, a group of scientists decided to analyze the spectra of globular clusters in the NGC 147, NGC 6822 and M33 galaxies living in the Local Group. Spectroscopic data was acquired with a HIRES spectrometer using the Keck I telescope (Hawaii) and UVES on the Very Large Telescope (Chile).
Analysis has shown that globular clusters in dwarf galaxies are prone to metal-poor objects, compared to their counterparts in the Milky Way halo. However, it was not possible to find a single globular cluster with metallicity below -2.5.
The distribution of metallicity of field stars and GC in NGC 147. For the second case, the bars were scaled according to the brightness of the V-band of each cluster
Scientists believe that the ratio of stellar alpha-elements to iron behaves differently, based on metallicity in dwarf galaxies and M33. Also, the findings suggest that the metal-poor clusters are endowed with alpha amplification at about the same level as the globular clusters in our galaxy.
It turned out that the alpha elements in the M33 globular clusters follow patterns similar to the Milky Way globular clusters. This suggests that the M33 halo was rapidly enriched, where nucleosynthesis of type II supernova dominates.
The researchers noted that with low metallicity models suggest that globular clusters in the Milky Way, dwarf galaxies and M33 experienced similar enrichment stories.