Unprecedented Number of Globular Clusters Discovered in Nearby Galaxy

Centaurus A is an elliptical galaxy situated about 13 million light-years from Earth. This shade composite picture reveals the lobes and jets emanating from the lively galaxy’s central black gap. Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

New treasure trove of globular clusters holds clues about galaxy evolution.

Using observations of the close by elliptical galaxy Centaurus A, a staff of astronomers led by the University of Arizona discovered an unprecedented quantity of potential globular clusters – previous, dense teams of 1000’s of stars that each one fashioned on the identical time.

A survey accomplished utilizing a mixture of floor and space-based telescopes yielded a treasure trove of beforehand unknown globular clusters – previous, dense teams of 1000’s of stars that each one fashioned on the identical time – in the outer areas of the elliptical galaxy Centaurus A. The work presents a big advance in understanding the structure and cosmological historical past of this galaxy and affords new insights into galaxy formation in normal and the distribution of darkish matter in the universe.

Allison Hughes, a doctoral pupil in the University of Arizona Department of Astronomy and Steward Observatory, is the primary creator of a peer-reviewed paper revealed in summarizing the findings, which was revealed in the Astrophysical Journal in June. She introduced the research Tuesday throughout an Astronomical Society of America press briefing. While the in-person AAS 239th assembly was canceled because of COVID-19 considerations, press briefings had been held nearly on Zoom.

Centaurus A, also referred to as NGC 5128, is a visually gorgeous, elliptical galaxy that includes a relativistic jet spewing from a supermassive black gap at its heart and spectacular streams of scattered stars left behind by previous collisions and mergers with smaller galaxies orbiting Centaurus A. Located in the constellation Centaurus, 13 million light-years from Earth, Centaurus A is simply too distant to permit astronomers to see particular person stars, however star clusters may be recognized and used as “fossil evidence” of the galaxy’s tumultuous evolution.

Hughes and her colleagues current a brand new catalog of roughly 40,000 globular cluster candidates in Centaurus A, recommending follow-up observations targeted on a set of 1,900 which might be almost definitely to be true globular clusters. The researchers surveyed globular cluster candidates out to a projected radius of roughly 150 kiloparsecs, almost half one million light-years from the galaxy’s heart. The information combines observations from the next sources: the Panoramic Imaging Survey of Centaurus and Sculptor, or PISCeS; Gaia, an area observatory of the European Space Agency; and the NOAO Source Catalog, which mixes publicly accessible photographs from telescopes in each hemispheres protecting almost your entire sky.

Centaurus A has been a number one goal for extragalactic globular cluster research because of its richness and proximity to Earth, however the majority of research have targeted on the internal 40 kiloparsecs (about 130,500 light-years) of the galaxy, Hughes defined, leaving the outer reaches of the galaxy largely unexplored. Ranking the candidates based mostly on the probability that they’re true globular clusters, the staff discovered that roughly 1,900 are extremely prone to be confirmed as such and ought to be the highest precedence for follow-up spectroscopic affirmation.

“We’re using the Gaia satellite, which mostly focuses on surveys within 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.”

Centaurus A’s construction tells astronomers that it went by way of a number of main mergers with different galaxies, resulting in its glob-like look with river-like areas which have many extra stars than the encompassing areas, Hughes stated. Providing the closest instance of an elliptical galaxy, Centaurus A affords astronomers a possibility to check up shut a galaxy that may be very not like our personal. The Milky Way, in addition to its closest neighbor, the Andromeda Galaxy, are each spiral galaxies. With their acquainted, pinwheel-like look, spiral galaxies might look like the “typical” galaxy, nevertheless it seems that their much less orderly elliptical cousins outnumber them in the cosmos.

“Centaurus A may look like an odd outlier, but that’s only because we can get close enough to see its nitty gritty details,” Hughes stated. “More likely than not, both elliptical and spiral galaxies like the Milky Way are messier than we realize as soon as we look a little bit deeper than just on the surface.”

Globular clusters function proof of processes that occurred a very long time in the past, Hughes stated.

“For example, if you see a line of these globular clusters that all have similar metallicity (chemical composition) and move with similar radial velocity, we know they must have come from the same dwarf galaxy or some similar object that collided with Centaurus A and is now in the process of being assimilated.”

Star clusters type from dense patches of fuel in the interstellar medium. Almost each galaxy has globular clusters, together with the Milky Way, which boasts round 150 of them, however most stars usually are not organized in such clumps. By finding out globular clusters, astronomers can collect clues in regards to the galaxy internet hosting them, equivalent to its mass, its historical past of interactions with close by galaxies and even the distribution of darkish matter inside, in line with Hughes.

“Globular clusters are interesting because they can be used as tracers of structures and processes in other galaxies where we can’t resolve individual stars,” Hughes stated. “They hold on to chemical signatures, such as the elemental composition of their individual stars, so they tell us something about the environment in which they formed.”

The researchers particularly appeared for globular clusters removed from the middle of the galaxy as a result of Centaurus A’s substructure hints at a big, undiscovered inhabitants of such clusters, Hughes defined. Previous observations had discovered slightly below 600 clusters in the extra central areas, however the outer areas of the galaxy had remained largely uncharted.

“We looked farther out and discovered more than 100 new clusters already, and most likely there are more, because we haven’t even finished processing the data,” Hughes stated. “We can then use that data to reconstruct the architecture and movements in that galaxy, and also figure out its mass. From that, we can eventually subtract all its stars and see what’s left – that invisible mass must be its dark matter.”

Reference: “NGC 5128 Globular Cluster Candidates Out to 150 kpc: A Comprehensive Catalog from Gaia and Ground-based Data” by Allison Ok. 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

(function(d, s, id){
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)) return;
js = d.createElement(s); js.id = id;
js.src = “//connect.facebook.net/en_US/sdk.js#xfbml=1&version=v2.6”;
fjs.parentNode.insertBefore(js, fjs);
}(document, ‘script’, ‘facebook-jssdk’));

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button