13 million light-years from Earth is the location of the elliptical galaxy Centaurus A. The image shows the jets and lobes from the central black hole. Credit: NASA/CXC/CfA/R.Kraft et al.
A survey using ground and space-based telescopes yielded a treasure trove of previously unknown globular clusters in the outer regions of the elliptical galaxy.
The first author of a peer-reviewed paper about the findings that were published in the Astrophysical Journal in June is Allison Hughes, a PhD student in the University of Arizona Department of Astronomy and Steward Observatory. She will present the study at the meeting.
A beautiful elliptical galaxy with a black hole at its center and a stream of stars left behind by past mergers with smaller galaxies, is called Centaurus A.
Hughes and her colleagues recommend follow-up observations of a set of 1,900 that are most likely to be true globular clusters after presenting a new catalog of approximately 40,000 candidates. The researchers surveyed candidates out to a projected radius of 150 kiloparsecs, which is half a million light-years away from the center of the galaxy. The data combines observations from the following sources: the PISCeS, the NOAO Source Catalog, and the space observatory of the European Space Agency.
.Centaurus A has been a leading target for extragalactic cluster studies due to its richness and proximity to Earth, but the majority of studies have focused on the inner 40 kiloparsecs of the galaxy. The team ranked the candidates based on their likelihood of being true globular clusters, and found that 1,900 are highly likely to be confirmed.
We're using the Gaia satellite to look at our own galaxy, the Milky Way, in a new way in that we link up its observations with telescopes on the ground, in this case the Magellan Clay telescope in Chile and the Anglo-Australian Telescope in Australia."
According to Hughes, Centaurus A's structure shows that it went through several major mergers with other galaxies, leading to its appearance with river-like regions that have many more stars than the surrounding areas. Astronomers have an opportunity to study up close a very different elliptical galaxy that is very similar to our own. The closest neighbor to the Milky Way is the AndromedaGalaxy. It turns out that spiral galaxies are not the "typical" one, but their less orderly elliptical cousins are.
"Centaurus Aurus may look like an odd outlier, but that's only because we can get close enough to see its details," Hughes said. The elliptical and spiral galaxies like the Milky Way are messier than we realize when we look a little bit deeper.
The evidence of processes that happened a long time ago can be found in the bicyle clusters.
If you see a line of clusters that all have the same metallicity and move with the same radial velocity, we know they must have come from the same dwarf galaxy or similar object that collided with Centaurus A.
There are dense patches of gas in the universe. The Milky Way has around 150 of them, but most stars are not arranged in such clumps. Analyzing the distribution of dark matter within a cluster can give clues to the history of interactions with nearby galaxies, according to Hughes.
"Globular clusters are interesting because they can be used as markers of processes and structures in other galaxies where we can't resolve individual stars," Hughes said. They tell us something about the environment in which they formed by holding on to chemical signatures.
The researchers looked for clusters far away from the center of the galaxy because of the large undiscovered population of such clusters.
Hughes said that they discovered more than 100 new clusters, and most likely there are more, because they haven't finished processing the data.
Hughes said that they can use that data to reconstruct the architecture and movements of that galaxy. We can eventually subtract all of its stars and see what's left.
Hughes will present her findings and implications of the research in a press conference on Tuesday at 1:45 p.m. MST.
Allison K. Hughes and her co-authors wrote about the candidates out to 150 kpc in the Astrophysical Journal. There is a book titled "10847/1538-4357/abf63c".
The Astrophysical Journal has information.
The treasure trove of globular clusters was retrieved from the internet on January 11.
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