by siphoning it off other less-massive companions.
Looking at NGC 6946, the GBT detected just the sort of filamentary structure that would be present in a cold flow.
However, it is also possible that in the past this galaxy had a close encounter and passed by its neighbours, leaving a ribbon of neutral atomic hydrogen in its wake.
If that were the case, however, there should be a small but observable population of stars in the filaments.
Further studies will help to confirm the nature of this observation and could shine light on the possible role that cold flows play in the evolution of galaxies.
The results are published in the Astronomical Journal.