Using radio telescopes, astronomers have found a radio galaxy with the structure of a drawn bow and arrow. The system RAD‑BAARG (Bow‑And‑Arrow Radio Galaxy) extends over as much as ∼1.8Mpc (luminous X-ray arc). It has a large, arc-like structure that differs from the typical radio galaxy morphology.
The work, published today in Monthly Notices of the Royal Astronomical Society: Letters, comes from an international team working with India’s RAD@home Astronomy Collaboratory, which used high-sensitivity imaging data from the Low‑Frequency Array (LOFAR) telescope.
“The structure of this source is unlike that of any radio galaxy I have seen in the last 25 years,” said lead author Dr. Ananda Hota, founder and director of RAD@home. “Its remarkable morphology appears to display signatures of interaction between relativistic radio plasma and a large‑scale shock generated during the galaxy’s infall into a nearby cluster environment.”
Radio galaxies are powered by central supermassive black holes that launch relativistic jets of plasma into the intergalactic medium. For RAD‑BAARG, this interaction with a bow shock, a region of compressed gas produced due to the supersonic motion of galaxies traveling into a cluster, appears to be associated with one of these jets. Interestingly, just as with the shock wave produced by a supersonic aircraft, the galaxy’s passage through the hot intracluster gas creates a large front that is ultimately illuminated in radio emission.
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The LOFAR images show that on one side, a jet creates a fan‑shaped glow and a huge arc stretching about 1.8 million light‑years. On the other side, the jet bends into an S‑shape before fading into a long, faint tail nearly as big. This uneven shape suggests that powerful forces in the galaxy’s environment are pushing and reshaping the plasma.
The host galaxy is in a dynamically active area with cluster-scale systems at similar distances. The team believes this unusual shape results from bulk gas motions and differences in environmental density, as well as shock compression effects.
Bow shocks around infalling galaxies are a common prediction of theoretical models and recent hydrodynamic simulations, but direct observational evidence has been limited. In these environments, the surrounding gas is extremely diffuse. Even modern X-ray observatories struggle to detect it clearly. In contrast, RAD-BAARG offers a clear radio view of this behavior.
“BAARG is exciting not just because of its striking bow‑and‑arrow shape, but because it sits in a complex multi‑halo environment where gas flows, infall and possible shocks can reshape radio plasma,” said co‑lead author Dr. Pratik Dabhade of the National Center for Nuclear Research in Poland. “LOFAR allows us to see this faint, low‑surface‑brightness emission in remarkable detail. With LoTSS DR3 and the future Square Kilometer Array Observatory (SKAO), we may find many more systems where radio galaxies reveal otherwise invisible interactions.”
Dr. Shubhrangshu Ghosh of SRM University Sikkim added: “The reported observation reveals the first direct imaging of characteristic arc‑shape morphology in radio frequency regarding supersonically infalling radio‑galaxy (most likely) onto a cluster medium, a spectacular textbook example of a large bow shock. Discovery of more such sources and their study during the SKAO era will provide much deeper insight about jet‑ambient medium interaction and consequent feedback processes.”
Beyond this unusual morphology, RAD‑BAARG also clearly demonstrates the duality of supermassive black hole outflows and their interactions with their environment. This especially shows how large-scale kinetic processes can reorganize cosmic material in a very different, bow-like signature over millions of light-years of space.
Journal Reference:
- Ananda Hota et al, RAD@home discovery of a bow-and-arrow radio galaxy tracing a ∼560 kpc bow-shock structure in a multihalo environment, Monthly Notices of the Royal Astronomical Society (2026). DOI: 10.1093/mnras/stag1033
