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 are some of the largest known structures in the known Universe. Current models suggest that these massive structures form as clumps of  and the galaxies that form within them are pulled together by gravity to form groups of dozens of galaxies, which in turn merge to form clusters of hundreds, even thousands. One such group is the  (Abell S636), located around 130 million light-years from Earth in the direction of the constellation  (the Air Pump).

This image was taken with the 570-megapixel Department of Energy-fabricated Dark Energy Camera (), mounted on the U.S. National Science Foundation (NSF)  at  in Chile, a Program of NSF NOIRLab. It captures only a portion of the 230 galaxies that so far have been found to make up the Antlia Cluster, as well as thousands of background galaxies. DECam’s ultra-deep view showcases the variety of galaxy types within and beyond the cluster .

Several Programs of NOIRLab (NOAO before 2019) have contributed observations of the Antlia Cluster over the past 20 years. Scientists from Chile have used both the Blanco telescope (with its predecessor camera MOSAIC II) and the , one half of the , funded in part by NSF and operated by NSF NOIRLab, to examine the cluster through the Antlia Cluster Project. In more recent years, researchers have investigated the cluster from space- and ground-based observatories. These combined efforts have revealed a dynamic menagerie of  within the cluster.

The Antlia Cluster is dominated by two massive  — NGC 3268 (center) and NGC 3258 (lower right). These central galaxies are surrounded by a number of faint  (see  showing the Altia Cluster in a different orientation). Researchers believe these two galaxies are in the process of merging, based on X-ray observations that revealed a  along the peak area of light between them. This may be evidence that the Antlia cluster is really two smaller clusters that are combining.

The cluster is rich in  — a type of disk galaxy that has little interstellar matter and thus little ongoing star formation — and also hosts some . A plethora of rarer, low-luminosity dwarf galaxies have been found in the cluster, including , compact ellipticals, and . The cluster may also contain  and the  sub-type, though further investigations are needed to confirm them.

Many of these galaxy types have only been identified within the past few decades because of advances in observational equipment and data analysis techniques that can better capture the low luminosity and relatively smaller size of these galaxies. Evaluating galaxy types allows astronomers to plot the fine details of , and some galaxies rich with dark matter provide further opportunities for astronomers to understand this mysterious substance that makes up 25% of the Universe.

The development of larger and more highly sensitized cameras like DECam allows astronomers to see the fainter details of these superstructures, such as the diffuse light between the cluster galaxies, which is a combination of  — the feeble glow of stars flung out into the gravitational field of the cluster by the churn of interacting galaxies — and faded light from the nearby Antlia Supernova Remnant .

’s upcoming  will be the first astronomical survey to provide scientists with the data they need to , unlocking clues to the distribution of dark matter around galaxy clusters and the evolutionary history of the Universe on large scales.

More information

, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the  (a facility of , , , , , and ), NSF Kitt Peak National Observatory (), NSF Cerro Tololo Inter-American Observatory (), the Community Science and Data Center (), and NSF–DOE  (in cooperation with ’s  National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy () under a cooperative agreement with  and is headquartered in Tucson, Arizona. 

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag (Kitt Peak) to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.

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