Reviewed by Lexie CornerJan 2 2025
NSF NOIRLab begins the New Year by showcasing an image of the Antlia Cluster captured by the Dark Energy Camera (DECam), installed on the U.S. National Science Foundation's Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile. The image highlights the diversity of galaxy types within the cluster's population.
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 a rich variety of 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-megapixel Department of Energy-fabricated Dark Energy Camera (DECam), mounted on the U.S. National Science Foundation (NSF) Víctor M. Blanco 4m Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF NOIRLab. It captures only a portion of the 230 of galaxies that so far have been found to make up the Antlia Cluster. DECam’s ultra-deep view showcases the variety of galaxies within and beyond the cluster in incredible detail. Image Credit: Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA.
Galaxy clusters are among the largest structures in the Universe. They are thought to form from clumps of dark matter, which draw galaxies together through gravity, creating groupings that merge into clusters containing hundreds or even thousands of galaxies. The Antlia Cluster (Abell S636) is located approximately 130 million light-years away in the constellation Antlia (the Air Pump).
This image, taken with the 570-megapixel DECam, shows a fraction of the 230 known galaxies in the Antlia Cluster, along with thousands of background galaxies. DECam’s ultra-deep view shows the various galaxy types within and outside the cluster in remarkable detail.
Over the past two decades, NOIRLab and its predecessor, NOAO, have contributed to observations of the Antlia Cluster. Chilean scientists have studied the cluster using the Blanco Telescope (previously equipped with the MOSAIC II camera) and the Gemini South Telescope, part of the International Gemini Observatory operated by NSF NOIRLab. These observations are part of the Antlia Cluster Project.
Recent studies using both space- and ground-based observatories have uncovered a range of unusual galaxy types within the cluster. The Antlia Cluster is dominated by two large elliptical galaxies, NGC 3268 and NGC 3258, surrounded by faint dwarf galaxies. X-ray observations suggest these two galaxies are merging, indicated by a "rope" of globular clusters connecting them. This could imply the cluster itself is the result of merging smaller clusters.
The cluster is rich in lenticular galaxies—disk galaxies with limited interstellar matter and low star formation activity—as well as irregular and low-luminosity dwarf galaxies. These include ultra-compact dwarfs, compact ellipticals, and blue compact dwarfs. Some rarer subtypes, such as dwarf spheroidal galaxies and ultra-diffuse galaxies, may also be present, though further study is needed.
Advances in observational tools and data analysis techniques have made it possible to identify these low-luminosity and compact galaxies, offering new insights into galaxy evolution. Some galaxies in the cluster, which are rich in dark matter, provide opportunities to study this elusive substance, which constitutes approximately 25 % of the Universe.
Large and sensitive instruments like DECam have allowed astronomers to explore subtler features of galaxy clusters, such as the diffuse light between galaxies. This light results from intracluster stars—those flung into the cluster's gravitational field by interacting galaxies—and contributions 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 provide detailed data on intracluster light in thousands of galaxy clusters. This information will shed light on the distribution of dark matter around clusters and the large-scale evolutionary history of the Universe.