Rare Giant Galaxies

AGC 192040 (left) and UGC 1382 (right)

Giant low-surface-brightness galaxies are rare and unusual members of the galactic menagerie. They host the largest galactic disks currently known, have baryonic masses of order 100 billion solar masses, and sport narrow, tightly wound spiral structures. The origins of these vast galaxies — they can be up to 10 times larger than the Milky Way — are unknown, though various theories involving mergers, accretion, and strange dark matter halos exist. Research also suggests that there may be a connection between these galaxies and compact ellipticals, which are small, dense, and contain old stars. In a recent article, a team led by Anna Saburova (Sternberg Astronomical Institute) investigated two giant low-surface-brightness galaxies with compact elliptical companions. In the image above, the colored circles represent the oxygen abundance at each location in AGC 192040 (left) and UGC 1382 (right). The red arrows point to the compact elliptical companions. Using the chemical abundance information to investigate possible formation mechanisms, Saburova and collaborators found that the two galaxies likely formed in different ways. UGC 1382 appears to be the result of multiple mergers, while AGC 192040 may have accreted gas from its halo or a galactic filament before undergoing a merger of its own. To learn more about this study of two rare galaxies, be sure to check out the full research article linked below!

By Kerry Hensley

Citation

“MUSE Study of Two Giant Low-Surface-Brightness Galaxies with Compact Satellites,” Anna S. Saburova et al 2026 ApJ 998 19. doi:10.3847/1538-4357/ae3139

Source: American Astronomical Society/AAS-Nova

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NuSTAR Observes a Triple Cluster Merger

A Chandra image of Abell 1750
Image credit: Scott Randall (Harvard ,br| CfA) & Esra Bulbul (MPE)
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Clusters of galaxies are the most massive gravitationally bound structures in the Universe, formed by the collapse of density peaks in the filamentary primordial dark matter structure. Investigations of their properties, like mass, number density, and size, provide powerful probes of fundamental cosmological parameters. However, accurate prediction of the mass of galaxy clusters requires deep understanding of the processes in the intra-cluster medium (ICM), a hot, diffuse gas that fills the volume between cluster member galaxies. The thermal state of the ICM is responsible for a large percentage of the pressure support that balances a cluster’s gravitational collapse, but other astrophysical processes may also be significant, including turbulence, magnetic fields and relativistic electron (cosmic-ray) pressure. The Abell 1750 galaxy cluster is bright in high-energy X-rays, possibly due to it being in the early stages of a merger of three galaxy clusters along a cosmic filament. NuSTAR observations over the past week were performed to probe non-thermal processes in the ICM. Combined with radio maps of the cluster and low-energy X-ray measurements by NASA’s Chandra X-ray Observatory, these NuSTAR observations will quantify the non-thermal pressure support in the cluster, improve measurements of cluster mass, and help to identify differences between merging and relaxed galaxy clusters.

Source: NASA's Nuclear Spectroscopic Telescope Array (NuSTAR)/Weekly Highlights

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