Centaurus A is an elliptical galaxy located about 13 million light-years from Earth. This color composite image exposes the lobes and jets originating from the active galaxys central great void. Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/ A.Weiss et al. (Submillimetre); NASA/CXC/CfA/ R.Kraft et al. (X-ray).
New bonanza of globular clusters holds ideas about galaxy evolution.
Utilizing observations of the close-by elliptical galaxy Centaurus A, a team of astronomers led by the University of Arizona discovered an extraordinary number of possible globular clusters– old, dense groups of thousands of stars that all formed at the same time.
A survey completed using a combination of ground and space-based telescopes yielded a bonanza of previously unknown globular clusters– old, thick groups of thousands of stars that all formed at the exact same time– in the outer regions of the elliptical galaxy Centaurus A. The work provides a substantial advance in comprehending the architecture and cosmological history of this galaxy and provides new insights into galaxy formation in basic and the distribution of dark matter in deep space.
Allison Hughes, a doctoral trainee in the University of Arizona Department of Astronomy and Steward Observatory, is the very first author of a peer-reviewed paper published in summarizing the findings, which was released in the Astrophysical Journal in June. She provided the study Tuesday throughout an Astronomical Society of America press instruction. While the in-person AAS 239th meeting was canceled due to COVID-19 issues, press instructions were held essentially on Zoom.
Offering the closest example of an elliptical galaxy, Centaurus A provides astronomers an opportunity to study up close a galaxy that is very unlike our own. The Milky Way, as well as its closest next-door neighbor, the Andromeda Galaxy, are both spiral galaxies. With their familiar, pinwheel-like appearance, spiral galaxies might seem like the “common” galaxy, however it turns out that their less orderly elliptical cousins outnumber them in the universes.
Practically every galaxy has globular clusters, including the Milky Way, which boasts around 150 of them, however a lot of stars are not organized in such clumps. By studying globular clusters, astronomers can gather clues about the galaxy hosting them, such as its mass, its history of interactions with nearby galaxies and even the circulation of dark matter within, according to Hughes.
Centaurus A, also referred to as NGC 5128, is an aesthetically sensational, elliptical galaxy featuring a relativistic jet gushing from a supermassive black hole at its center and magnificent streams of scattered stars left by past crashes and mergers with smaller galaxies orbiting Centaurus A. Located in the constellation Centaurus, 13 million light-years from Earth, Centaurus A is too far away to enable astronomers to see individual stars, but star clusters can be identified and used as “fossil proof” of the galaxys tumultuous advancement.
Hughes and her coworkers present a brand-new catalog of roughly 40,000 globular cluster prospects in Centaurus A, recommending follow-up observations concentrated on a set of 1,900 that are most likely to be true globular clusters. The researchers surveyed globular cluster candidates out to a projected radius of around 150 kiloparsecs, almost half a million light-years from the galaxys center. The data combines observations from the following sources: the Panoramic Imaging Survey of Centaurus and Sculptor, or PISCeS; Gaia, a space observatory of the European Space Agency; and the NOAO Source Catalog, which combines publicly available images from telescopes in both hemispheres covering almost the entire sky.
Centaurus A has been a leading target for extragalactic globular cluster research studies due to its richness and distance to Earth, however the bulk of research studies have concentrated on the inner 40 kiloparsecs (about 130,500 light-years) of the galaxy, Hughes discussed, leaving the external reaches of the galaxy largely unexplored. Ranking the candidates based upon the possibility that they hold true globular clusters, the team found that around 1,900 are extremely most likely to be confirmed as such and need to be the greatest concern for follow-up spectroscopic confirmation.
” Were utilizing the Gaia satellite, which mostly focuses on studies within our own galaxy, the Milky Way, in a brand-new method in that we link its observations with telescopes on the ground, in this case the Magellan Clay telescope in Chile and the Anglo-Australian Telescope in Australia.”.
Centaurus As structure informs astronomers that it went through numerous significant mergers with other galaxies, leading to its glob-like appearance with river-like areas that have much more stars than the surrounding locations, Hughes said. Supplying the closest example of an elliptical galaxy, Centaurus A provides astronomers an opportunity to study up close a galaxy that is extremely unlike our own. The Milky Way, as well as its closest neighbor, the Andromeda Galaxy, are both spiral nebula. With their familiar, pinwheel-like appearance, spiral nebula might appear like the “common” galaxy, but it ends up that their less orderly elliptical cousins outnumber them in the cosmos.
” Centaurus A may appear like an odd outlier, however thats just because we can get close enough to see its nitty gritty details,” Hughes said. “More likely than not, both elliptical and spiral nebula like the Milky Way are messier than we realize as soon as we look a little bit much deeper than simply on the surface.”.
Globular clusters work as proof of procedures that happened a long period of time back, Hughes stated.
” For example, if you see a line of these globular clusters that all have similar metallicity (chemical structure) and move with similar radial speed, we understand they must have originated from the same dwarf galaxy or some comparable item that hit Centaurus A and is now in the procedure of being assimilated.”.
Star clusters form from dense patches of gas in the interstellar medium. Almost every galaxy has globular clusters, consisting of the Milky Way, which boasts around 150 of them, however the majority of stars are not organized in such clumps. By studying globular clusters, astronomers can gather ideas about the galaxy hosting them, such as its mass, its history of interactions with close-by galaxies and even the circulation of dark matter within, according to Hughes.
” Globular clusters are interesting because they can be used as tracers of structures and processes in other galaxies where we cant resolve individual stars,” Hughes said. “They hang on to chemical signatures, such as the elemental structure of their individual stars, so they inform us something about the environment in which they formed.”.
The scientists particularly looked for globular clusters far from the center of the galaxy due to the fact that Centaurus As base mean a large, undiscovered population of such clusters, Hughes discussed. Previous observations had discovered just under 600 clusters in the more central regions, but the outer areas of the galaxy had actually stayed mainly uncharted.
” We looked further out and discovered more than 100 new clusters already, and more than likely there are more, since we have not even completed processing the data,” Hughes stated. “We can then utilize that data to rebuild the architecture and movements in that galaxy, and likewise find out its mass. From that, we can ultimately subtract all its stars and see whats left– that unnoticeable mass must be its dark matter.”.
Recommendation: “NGC 5128 Globular Cluster Candidates Out to 150 kpc: A Comprehensive Catalog from Gaia and Ground-based Data” by Allison K. Hughes, David J. Sand, Anil Seth, Jay Strader, Karina Voggel, Antoine Dumont, Denija Crnojević, Nelson Caldwell, Duncan A. Forbes, Joshua D. Simon, Puragra Guhathakurta and Elisa Toloba, 9 June 2021, The Astrophysical Journal.DOI: 10.3847/ 1538-4357/ abf63c.