Astronomers study star cluster KMHK 1762 in the Large Magellanic Cloud

Image approximately 4′ across in g-band centered on KMHK 1762. Red circle indicates radius of 0.5′ star cluster. Credit: Gatto et al., 2022.

Using the VLT Survey Telescope (VST), European astronomers have studied a particular star cluster in the Large Magellanic Cloud (LMC), known as KMHK 1762. The results of the study have been published July 19 on

KMHK 1762 (also known as OHSC 37) is a star cluster in the LMC. The cluster has a metallicity at a level of -0.91 and is estimated to be around 2.7 billion years old. However, an analysis of the color-magnitude diagram (CMD) of KMHK 1762 suggests that the cluster may be older than currently estimated.

A team of astronomers led by Massimiliano Gatto from the Capodimonte Astronomical Observatory in Naples, Italy, investigated this question, speculating that KMHK 1762 might be a rare case of a star cluster in the age gap. says LMC. Previous LMC observations have shown that this galaxy has an almost complete absence of star clusters between 4 and 10 billion years old. Within this age gap, only two confirmed star clusters have been identified so far.

Gatto’s team analyzed deep optical photometry of KMHK 1762 obtained with VST as part of the Yes, Magellanic Clouds Again (YMCA) survey. The study was supplemented by data from ESA’s Gaia satellite.

“In this letter, we report the result of our new study of KMHK 1762 SC [star cluster]based on deep and accurate YMCA photometry, supplemented with parallaxes and proper motions (PM) from Gaia Early Data Release 3 (EDR3),” the researchers wrote.

According to the new study, the appropriate age of KMHK 1762 should be higher than previously thought. Based on shallower photometry, astronomers estimate this cluster to be around 5.5 billion years old. This means that KMHK 1762 is the third star cluster in the LMC age gap, in addition to clusters ESO121-03 and KMHK 1592.

Observations revealed that KMHK 1762 has a redness of about 0.08 mag and its metallicity is at a level of -0.65. The CMD shows a cluster of stars identified as Main Sequence Turn-off (MSTO), Subgiant Branch (SGB) stars, as well as a few stars in the Red Giant Branch (RGB) and Red Group (RC ).

The discovery made by the authors of the paper calls into question the existence of star cluster age discrepancy in LMC. They suggest that the increased number of confirmed or suspected clusters formed during the age-gap period indicates that the age-gap may be an observational bias, due to the combination of shallow photometry and a limited survey of the LMC’s outer regions.

“In fact, most of the work devoted to the search for undiscovered star clusters has been concentrated in the central regions of the LMC leaving the periphery (i.e. d > 4 kpc) quite unexplored and has been conducted based on shallow photometric surveys, allowing researchers to detect only star clusters smaller than ∼1–1.5 Gyrs,” the researchers concluded.

Italian astronomers discover new star cluster

More information:
M. Gatto et al, KMHK 1762: Another star cluster in the age gap of the Large Magellanic Cloud. arXiv:2207.09478v1 [astro-ph.GA]

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Quote: Astronomers investigate star cluster KMHK 1762 in the Large Magellanic Cloud (2022, July 28) Retrieved July 29, 2022 from -kmhk-large.html

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