A survey completed working with a mixture of floor and area-centered telescopes yielded a treasure trove of previously mysterious globular clusters — old, dense groups of countless numbers of stars that all fashioned at the similar time — in the outer areas of the elliptical galaxy Centaurus A. The operate presents a significant advance in understanding the architecture and cosmological heritage of this galaxy and presents new insights into galaxy development in common and the distribution of dark subject in the universe.
Allison Hughes, a doctoral scholar in the College of Arizona Department of Astronomy and Steward Observatory, is the first writer of a peer-reviewed paper summarizing the results that was printed in the Astrophysical Journal in June. She will present the research through a digital press briefing at the 239th Meeting of the Astronomical Modern society of The us Tuesday.
Centaurus A, also recognized as NGC 5128, is a visually breathtaking, elliptical galaxy featuring a relativistic jet spewing from a supermassive black hole at its centre and magnificent streams of scattered stars remaining behind by past collisions and mergers with smaller galaxies orbiting Centaurus A. Positioned in the constellation Centaurus, 13 million mild-years from Earth, Centaurus A is too considerably away to let astronomers to see particular person stars, but star clusters can be recognized as this kind of and employed as “fossil proof” of the galaxy’s tumultuous evolution.
Hughes and her colleagues current a new catalog of somewhere around 40,000 globular cluster candidates in Centaurus A, recommending follow-up observations targeted on a set of 1,900 that are most most likely to be true globular clusters. The researchers surveyed globular cluster candidates out to a projected radius of close to 150 kiloparsecs, nearly half a million light-years from the galaxy’s heart. The information brings together observations from the subsequent resources: the Panoramic Imaging Survey of Centaurus and Sculptor, or PISCeS Gaia, a place observatory of the European Place Agency, and the NOAO Resource Catalog, which combines publicly accessible images from telescopes in the two hemispheres masking virtually the full sky.
.Centaurus A has been a foremost concentrate on for extragalactic globular cluster studies because of to its richness and proximity to Earth, but the the vast majority of experiments have centered on the internal 40 kiloparsecs (about 130,500 light-a long time) of the galaxy, Hughes spelled out, leaving the outer reaches of the galaxy mostly unexplored. Position the candidates primarily based on the chance that they are accurate globular clusters, the crew uncovered that somewhere around 1,900 are hugely probable to be verified as such and must be the greatest precedence for observe-up spectroscopic confirmation.
“We’re applying the Gaia satellite, which generally focuses on surveys within just our individual galaxy, the Milky Way, in a new way in that we connection up its observations with telescopes on the ground, in this scenario the Magellan Clay telescope in Chile and the Anglo-Australian Telescope in Australia.”
Centaurus A’s construction tells astronomers that it went by means of quite a few main mergers with other galaxies, major to its glob-like visual appearance with river-like locations that have lots of additional stars than the encompassing parts, Hughes reported. Providing the closest illustration of an elliptical galaxy, Centaurus A gives astronomers an possibility to analyze up near a galaxy that is extremely in contrast to our own. The Milky Way, as nicely as its closest neighbor, the Andromeda Galaxy, are both spiral galaxies. With their acquainted, pinwheel-like visual appearance, spiral galaxies might seem like the “usual” galaxy, but it turns out that their significantly less orderly elliptical cousins outnumber them in the cosmos.
“Centaurus A might look like an odd outlier, but which is only due to the fact we can get close ample to see its nitty gritty facts,” Hughes said. “Far more probably than not, the two elliptical and spiral galaxies like the Milky Way are messier than we recognize as soon as we seem a tiny bit deeper than just on the floor.”
Globular clusters provide as proof of processes that transpired a extensive time back, Hughes explained.
“For instance, if you see a line of these globular clusters that all have similar metallicity (chemical composition) and shift with very similar radial velocity, we know they have to have occur from the similar dwarf galaxy or some identical object that collided with Centaurus A and is now in the procedure of remaining assimilated.”
Star clusters kind from dense patches of gasoline in the interstellar medium. Just about just about every galaxy has globular clusters, together with the Milky Way, which features about 150 of them, but most stars are not arranged in this kind of clumps. By finding out globular clusters, astronomers can gather clues about the galaxy web hosting them, these types of as its mass, its background of interactions with nearby galaxies and even the distribution of darkish matter inside of, in accordance to Hughes.
“Globular clusters are interesting because they can be made use of as tracers of constructions and processes in other galaxies where we are not able to solve particular person stars,” Hughes stated. “They keep on to chemical signatures, such as the elemental composition of their person stars, so they notify us a little something about the setting in which they shaped.”
The researchers specifically looked for globular clusters significantly from the center of the galaxy simply because Centaurus A’s substructure hints at a huge, undiscovered inhabitants of these clusters, Hughes described. Previous observations experienced found just less than 600 clusters in the a lot more central locations, but the outer regions of the galaxy experienced remained mainly uncharted.
“We looked farther out and uncovered more than 100 new clusters already, and most probable there are much more, for the reason that we have not even finished processing the details,” Hughes explained.
“We can then use that info to reconstruct the architecture and actions in that galaxy, and also determine out its mass,” Hughes stated. “From that we can inevitably subtract all its stars and see what is left — that invisible mass have to be its darkish subject.”