I found a weird thing with ALMA and want to crowdsource some explanations

Abstract: Post-starburst galaxies (galaxies that were rapidly forming stars before quickly quenching star formation <1Gyr ago) have proven to be useful probes of the way that galaxies change in morphology and become quiescent. While the "burst" in nearby post-starbursts generally contributed only ~5% to the pre-existing stellar mass, we have identified a population of z~0.5-1 post-starbursts that appear to have just quenched their primary epoch of star formation. Followup ALMA observations have shown a huge variety in their molecular gas masses and fractions, suggesting a diversity of pathways to quiescence. In an unexpected surprise, I have found vast extended structures of molecular gas around a third of the detected galaxies in the sample, with nearly half of the total molecular mass extending up to ~50kpc outside the host galaxies. While I've come up with a few possible explanations for the origins of these highly-extended features, none of them is completely satisfying at this point. I will end by outlining some of our proposed followup observations and solicit wild speculation about any scenarios we haven't yet considered.