Study Identifies Stars With Fewer Metals In Omega Centauri Cluster

By analyzing spectroscopic data, astronomers have investigated the globular cluster Omega Centauri, with the aim of finding a population of stars with very low metallicity. The study resulted in the detection of the 11 poorest metal stars in this group. The finding is reported in an article published April 20 in arXiv.

Observations of globular clusters (GC) in the Milky Way galaxy are of great importance to astronomers, as they are among the oldest objects in the universe. Therefore, they are perceived as natural laboratories for the study of stellar evolution processes.

Located some 15,800 light years away, Omega Centauri (also known as NGC 5139) is the brightest and most massive galactic GC. Observations show that the group is chemically diverse, and astronomers assume it can harbor up to 15 unique star populations. The stars in Omega Centauri exhibit much higher metallic dispersions compared to other galactic GCs.

Although Omega Centauri has been the target of many studies, its origin and enrichment story remain an open question. This cluster is believed to have originated as a nuclear core of a dwarf galaxy now disrupted by the tide. Finding and studying the metal’s poorest stars in the cluster could verify whether this hypothesis is true.

So, a team of astronomers led by Christian Johnson from the Space Telescope Science Institute in Baltimore, Maryland, investigated nearly 400 of the bluest red giant branch (RGB) stars in Omega Centauri, hoping to find the population. poorer stellar in cluster metals. For this purpose, they used the Michigan-Magellan Fiber System (M2FS) and the MSpec spectrograph mounted on the Magellan-Clay 6.5m telescope at the Las Campanas Observatory.

“We present [Fe/H] measurements, based on high-resolution M2FS spectra, for 395 giants in the massive Omega Centauri globular cluster. The targets were chosen to reside in the blue half of the RGB in an effort to find the metal-poorest stars in the cluster, “the astronomers wrote in the document.

The study found 11 stars with metallicities ranging from −2.30 to −2.52, hence the majority of the metal-poor stars in Omega Centauri. The newly discovered stars are significantly poorer in metals than the dominant cluster population with metallicities of around -1.7, and their intermediate metallicity group with metallicities at a level of approximately -1.5.

According to the document, Omega Centauri’s metal-poorer stars appear to be centrally concentrated, and may also be limited to a narrow declination plane. However, it was observed that these stars do not appear to exhibit peculiar kinematic properties that distinguish them from the most metal-rich populations in the cluster.

Astronomers ponder some possible scenarios that could explain the presence of such metal-poor stars in Omega Centauri. They assume that this population may be the result of early star formation in the unenriched primordial cloud, capture of surrounding field stars (if the cluster formed in a dwarf galaxy), or an early merger between Omega Centauri and a pre-existing metal. but poor substructure. According to the authors of the article, the merger scenario is the most plausible.

“The fusion subgroup model may have the best chance of describing the scarcity of very metal-poor stars in other clusters, the possibly reduced light element spreading for stars with [Fe/H]

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