Globular cluster NGC 6558 explored with Gemini Observatory and Hubble Space Telescope

Utilizing the Gemini Observatory and the Hubble Area Telescope (HST), a global crew of astronomers has investigated a Galactic globular cluster often known as NGC 6558. Outcomes of the brand new research, published July 22 on the pre-print server arXiv, ship vital insights into the properties of this cluster.

Globular clusters (GCs) are collections of tightly certain stars orbiting galaxies. Astronomers understand them as pure laboratories enabling research on the evolution of stars and galaxies. Specifically, globular clusters might assist researchers to raised perceive the formation historical past and evolution of early-type galaxies, because the origin of GCs appears to be carefully linked to durations of intense star formation.

NGC 6558 (often known as GCL 89 or ESO 456-SC62) is a Galactic bulge globular cluster positioned some 24,100 mild years away within the constellation Sagittarius, with an angular dimension of about 5.4 x 5.4 arcminutes. Earlier observations have discovered that NGC 6558 has a metallicity at a degree of -1.32 dex and urged that it might be one of many oldest objects within the Milky Way.

Nevertheless, resulting from excessive reddening, the area of NGC 6558 presents challenges in deriving correct parameters. A gaggle of astronomers led by Stefano Souza of the College of São Paulo in Brazil, has now carried out near-infrared and optical photometry of this cluster. For this objective, they employed Gemini Observatory’s Gemini-South telescope and HST’s Superior Digital camera for Surveys (ACS).

“We goal to refine the basic parameters of NGC 6558, using high-quality Gemini-South/GSAOI and HST/ACS photometries. Moreover, we intend to analyze its position within the formation of the Galactic bulge,” the researchers clarify.

The collected high-quality photometric information allowed the crew to derive elementary parameters of NGC 6558. By eradicating as a lot as potential of the Galactic bulge discipline star contamination, the astronomers have been capable of receive essentially the most correct outcomes than ever earlier than.

The observations discovered that NGC 6558 is positioned about 27,400 mild years away. That is farther than distances obtained by earlier research, which urged between 20,500 and 26,900 mild years.

The reddening of NGC 6558 was measured to be at a degree of 0.34. The astronomers underline that that is the bottom worth relative to the accessible literature, obtained with the differential reddening correction primarily based on reference stars much less contaminated by discipline stars.

Based mostly on the obtained information, the authors of the paper estimate that NGC 6558 is a few 13 billion years outdated. They be aware that this age is appropriate with different clusters with related metallicity and a blue horizontal department within the Galactic bulge.

Summing up the outcomes, the researchers conclude that NGC 6558, mixed with different reasonably metal-poor GCs, counsel that the formation time of this inhabitants is as late as 13.62 billion years and with a chemical enrichment 10-times sooner than the remainder of the Milky Way.

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