Russian Federation
"Odd radio circles" up to 300 kpc in diameter, containing dozens of spherical clumps ~15 kpc in di-ameter were detected. Warm gas in the radio circles emits in the UV lines of a number of ions (O, Mg, Ne) with a temperature of ~104 K, broadened by the gas dynamics (~200 km/s) caused by the shock wave. Emission in the optical and near-IR ranges is associated with the stellar continuum. The radio circle may be formed by supernova shock waves amplified by the stellar wind of blue stars in a stellar stream ≥109 years old, containing ≥3∙108 stars, formed by a galaxy with a mass of ~1010 M○. Star formation in a stellar stream can be initiated by gas raked by a shock wave (flowing into its tail) formed around the gas corona of a satellite galaxy moving in intergalactic gas.
odd radio circles, star streams, supernovae, stellar wind
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