Galaxy clusters rank among the most significant known structures in the Universe. Current models suggest they form when clumps of dark matter pull galaxies together, merging smaller groups into vast clusters containing hundreds or even thousands of galaxies. One such group is the Antlia Cluster (Abell S636), located roughly 130 million light-years away in the constellation Antlia (the Air Pump).
Credit: Dark Energy Survey Image processing: R. Colombari & M. Zamani (NSF NOIRLab)
The Antlia Cluster (Abell S636) is a group of at least 230 galaxies located about 130 million light-years away in the direction of the constellation Antlia (the Air Pump). It hosts various galaxy types, including lenticular galaxies, irregular galaxies, and ultra-compact dwarfs. The cluster is dominated by two massive elliptical galaxies — NGC 3268 (center) and NGC 3258 (lower right). This image was taken with the 570-mp Department of Energy-fabricated Dark Energy Camera (DECam), mounted on the U.S. National Science Foundation (NSF) Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF NOIRLab.
This new image comes from the 570-megapixel Dark Energy Camera (DECam), developed by the U.S. Department of Energy and mounted on the National Science Foundation’s (NSF) Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile, a program of NSF’s NOIRLab. Although it captures only part of the 230 known galaxies in the Antlia Cluster, it also reveals thousands of more distant background galaxies. DECam’s exceptional sensitivity highlights galaxy types in and around the cluster.
Ongoing Research Efforts
Over the past two decades, several projects at NOIRLab (formerly NOAO) have observed the Antlia Cluster. Chilean scientists have used the Blanco Telescope (fitted previously with the MOSAIC II camera) and the Gemini South telescope — part of the International Gemini Observatory, funded in part by NSF and operated by NSF’s NOIRLab — to study the cluster through the Antlia Cluster Project. Recent investigations from ground- and space-based observatories have revealed a wide range of rarer galaxy types in this dynamic environment.
Two massive elliptical galaxies dominate the cluster: NGC 3268 (at the center) and NGC 3258 (near the lower right). Numerous faint dwarf galaxies lie nearby. Researchers believe these two galaxies may be merging, as X-ray observations point to a “rope” of globular clusters running along the brightest region between them. This could mean the Antlia Cluster is formed from two smaller clusters combined.
A diversity of galaxy types
The Antlia Cluster contains many lenticular galaxies with disk-like shapes but relatively little interstellar material or star formation. Some irregular galaxies also inhabit the cluster. Numerous low-luminosity dwarf galaxies, including ultra-compact dwarfs, compact ellipticals, and blue compact dwarfs, have been discovered here. Dwarf spheroidal and ultra-diffuse galaxies may also be present, though researchers still need further observations to confirm them.
Many of these galaxy types have only been identified in recent decades, thanks to more advanced equipment and data analysis methods that reveal faint, small-scale objects. Studying these galaxies helps astronomers map out the finer details of how galaxies evolve while also shedding light on dark matter. This substance accounts for about 25% of the Universe’s total mass and energy.
Future surveys and intracluster light
Improved technology, such as more prominent and sensitive instruments like DECam, allows astronomers to detect faint details of galaxy clusters, including diffuse light between cluster members. This glow is partly intracluster light from stars torn free by interactions and partly residual light from the nearby Antlia Supernova Remnant, discovered in 2002.
The upcoming Legacy Survey of Space and Time (LSST) at the NSF–DOE Vera C. Rubin Observatory will soon provide the data to detect intracluster light in thousands of galaxy clusters. This will offer unprecedented insights into the distribution of dark matter in galaxy clusters and help astronomers piece together the large-scale evolutionary history of the Universe.
More Information
NSF’s NOIRLab is the U.S. National Science Foundation center for ground-based optical-infrared astronomy. It operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF’s Kitt Peak National Observatory (KPNO), NSF’s Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and the NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). NOIRLab is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.
