Observations explore globular cluster system of ultra-diffuse galaxy VCC 615
Stacked F814W ACS image of VCC 615, with a total exposure time of 11×1,200 s. Credit: Mihos et al, 2024
Astronomers have employed the Hubble Space Telescope (HST) to observe an ultra-diffuse galaxy known as VCC 615. Results of the observational campaign, presented in a paper posted Dec. 2 to the preprint server arXiv, yield important insights into the globular cluster system of this galaxy.
Globular clusters (GCs) are collections of tightly bound stars orbiting galaxies. Astronomers perceive them as natural laboratories enabling studies on the evolution of stars and galaxies. In particular, GCs could help researchers to better understand the formation history and evolution of early-type galaxies, as the origin of GCs seems to be closely linked to periods of intense star formation.
VCC 615 is an ultra-diffuse galaxy located on the outskirts of the Virgo Cluster, some 57.7 million light years away. The galaxy has an effective radius of approximately 7,300 light years, and its stellar mass is estimated to be 73 million solar masses.
Recently, a team of astronomers led by J. Christopher Mihos of the Case Western Reserve University in Cleveland, Ohio, has used HST's Advanced Camera for Surveys (ACS) to investigate the GC system in VCC 615, hoping that it could shed more light on the properties of this galaxy.
"Our Hubble imaging lets us construct a very clean and deep sample of globular cluster candidates that extends more than 90% down the globular cluster luminosity function, while simultaneously rejecting background galaxies that would be unresolved contaminants in ground-based imaging," the researchers explained.
Mihos's team managed to identify 22 GC candidates and the galaxy's compact nucleus in the ACS field of view, down to a limiting magnitude of 24.0. Further inspection of the imagery found that 15 of these GC candidates are located within 1.5 half-light radii from the center of VCC 615.
According to the paper, six identified GC candidates of VCC 615 remain unresolved, while for the other 16, the astronomers have determined half-light radii spanning within the range 6.5–55.4 light years.
All in all, the total globular cluster population for VCC 615 was estimated to be 25.1. This yields a globular cluster specific frequency at a level of 55.5, which is quite large when compared to typical dwarf galaxies with similar luminosity. Therefore, these findings suggest a large mass-to-light ratio for VCC 615.
The study also found that VCC 615 has a total mass between 90 and 160 billion solar masses, and that the identified compact nucleus is photometrically distinct from the galaxy's GC population. The authors of the paper suppose that this nucleus may be tidally stripped from VCC 615 in the future to form a new ultracompact dwarf galaxy.
More information: J. Christopher Mihos et al, The Globular Cluster System of the Virgo Cluster Ultradiffuse Galaxy VCC 615, arXiv (2024). DOI: 10.48550/arxiv.2412.01730
Journal information: arXiv
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Citation: Astronomers explore globular cluster system of ultra-diffuse galaxy VCC 615 (2024, December 10) retrieved 10 December 2024 from https://phys.org/news/2024-12-astronomers-explore-globular-cluster-ultra.html
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