Neutral hydrogen observations of the spiral galaxies NGC 6221 and 6215 with the Australia Telescope Compact Array (ATCA) reveal a wide, two-stranded bridge of at least 3 10 8 M which can be traced between the two galaxies over a projected distance of 100 kpc. The velocity gradient of the H I bridge provides a rough estimate for the time since the encounter of 500 Myr. For NGC 6221, the brightest and most massive galaxy of the group, we derive a dynamical mass of M tot = 8 10 10 M , while its companion NGC 6215 has a mass of only M tot 2 10 9 M . Further, we find three low-surface-brightness dwarf galaxies (Dwarfs 1, 2 and 3) in the neighbourhood of NGC 6221/15 with H I masses of 3.3, 0.6 and 0.3 10 8 M , respectively. The smallest, previously uncatalogued galaxy, Dwarf 3, lies between NGC 6221 and 6215, and may have formed out of bridge material.
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Koribalski et al. (2004) studied this question.
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