Utilizing the Keck Observatory, astronomers from the Radboud College within the Netherlands and elsewhere have carried out spectroscopic observations of a younger huge cluster generally known as NGC 1569-B. Outcomes of the observational marketing campaign, revealed September 23 on the arXiv pre-print server, yield essential insights into the chemical composition of this cluster.
Normally, younger huge clusters (YMCs) are dense aggregates of younger stars that type the elemental constructing blocks of galaxies. Learning their chemical composition may present important info relating to stellar populations.
Estimated to be 15–25 million years previous, NGC 1569-B is a YMC within the dwarf irregular galaxy NGC 1569, positioned some 6,000 light years away from the Earth. With a mass of about 440,000 solar masses, NGC 1569-B is extra huge than any of the younger clusters within the Milky Way or Giant Magellanic Cloud (LMC). Such huge clusters are uncommon in our galaxy and even within the Native Group.
A gaggle of astronomers led by Anastasia Gvozdenko investigated NGC 1569-B with the high-resolution echelle spectrometer (HIRES) on the Keck I 10-m telescope on Mauna Kea in Hawaii. The primary goal of their examine was to carry out an in depth chemical abundance evaluation of this cluster.
“We carried out a high-resolution IL [integrated-light] spectrum evaluation of the YMC NGC 1569-B. That is the primary detailed abundance examine of this YMC utilizing the complete optical wavelength vary,” the researchers wrote within the paper.
The observations discovered that NGC 1569-B is barely metal-poor as its metallicity was measured to be about −0.77. It showcases alpha and nearly all of the iron-peak ingredient abundance ratios typical for Milky Way thick disk or LMC bar stars. What’s noteworthy is that the cluster has a very excessive titanium abundance of roughly 0.49.
Moreover, the outcomes point out that NGC 1569-B has a comparatively excessive barium-to-iron abundance ratio. This could possibly be attributable to the contribution from massive stars, nevertheless no proof supporting this principle has been discovered.
One other unexpectedly excessive abundance ratio was discovered to be scandium to iron. The authors of the paper are unable to elucidate this consequence in the intervening time, subsequently additional research of the chemical composition of NGC 1569-B are required to discover a believable speculation.
Summing up the findings, the researchers famous that the chemical abundances of NGC 1569-B typically resemble these of one other YMC that was the topic of just lately revealed research—NGC 1705-1.
“The composition of NGC 1569-B resembles the stellar populations of the YMC NGC 1705-1, positioned in a blue compact dwarf galaxy. The 2 YMCs agree with regard to alpha-elements and nearly all of the iron-peak components, apart from Sc and Ba, that are extraordinarily super-solar in NGC 1569-B—and better than in any YMC studied to date,” the astronomers concluded.
Anastasia Gvozdenko, Søren S. Larsen, Michael A. Beasley, Jean Brodie, Chemical composition of the younger huge cluster NGC 1569-B. arXiv:2209.11779v1 [astro-ph.GA], arxiv.org/abs/2209.11779
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