4′ × 4′ box at the VVV DR4 symbol of Gran 5. The seven spectroscopic goal stars are marked via inexperienced circles. The yellow circle represents the half-light radius (0.94′) of Gran 5. Credit score: Lim et al., 2024.
The use of the Gemini-South telescope, astronomers have carried out high-resolution near-infrared spectroscopy of stars in a Galactic globular cluster referred to as Gran 5. They discovered that this cluster harbors two stellar populations with other metallicities. The discovering used to be reported in a paper printed October 28 at the pre-print server arXiv.
Globular clusters (GCs) are collections of tightly certain stars orbiting galaxies. Astronomers understand them as herbal laboratories enabling research at the evolution of stars and galaxies. Specifically, globular clusters may lend a hand researchers to raised perceive the formation historical past and evolution of early-type galaxies, because the foundation of GCs appears to be carefully connected to classes of intense big name formation.
Gran 5 is a newly found out low-mass GC situated some 14,600 gentle years away, very with reference to the Galactic heart. The cluster has a mass of about 22,900 sun plenty and is thought to be an accreted object related to the Gaia–Enceladus–Sausage kinematic construction within the Milky Means’s halo.
Aiming to shed extra gentle on stellar populations of Gran 5 and to unveil their detailed chemical homes, a group of astronomers led via Dongwook Lim of the Yonsei College in Seoul, South Korea, investigated seven stars of this cluster with the Immersion Grating Infrared Spectrometer (IGRINS).
“We carried out high-resolution near-infrared spectroscopy on seven stars within the box of Gran 5 the use of IGRINS at the Gemini-South telescope,” the researchers wrote within the paper.
According to the spectroscopy of the seven stars, Lim’s group recognized six stars as cluster participants, whilst one big name used to be excluded because of its considerably other radial speed. Those six stars have heliocentric radial velocities of about -60 km/s and occasional metallicities at a degree of -0.65 dex, confirming that Gran 5 is certainly a globular cluster.
On the other hand, the learn about discovered that those investigated stars may also be divided into two teams with other metallicities, with imply values of −0.76 dex and −0.55 dex for each and every team. For the reason that those two teams don’t display any tendency in opposition to heliocentric radial velocities or atmospheric parameters, the astronomers suppose that Gran 5 is composed of 2 stellar populations with other metallicities.
The authors of the paper notice that their learn about marks the primary detection of 2 stellar populations with other metallicities in a low-mass globular cluster. They upload that the derived chemo-dynamical homes of Gran 5 counsel that it’s not related to the Gaia–Enceladus–Sausage construction however belongs to the Galactic bulge or disk.
Summing up the consequences, the researchers conclude that the seen metallicity variation of Gran 5 can have arisen from other processes, or that it should have misplaced quite a lot of mass all through its evolution.
Additional information:
Dongwook Lim et al, Two stellar populations with other metallicities within the low-mass globular cluster Gran 5, arXiv (2024). DOI: 10.48550/arxiv.2410.21578
Magazine data:
arXiv
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Globular cluster Gran 5 hosts two stellar populations, learn about reveals (2024, November 5)
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