gas around the galaxies (Putman et al. 2012). Hence, it may be better to search for the cold-mode accreting neutral gas well outside the galactic disks, by searching for signal from a large volume around the central galaxies. Here we attempt to perform exactly this search by analysing the data taken as part of the Bluedisk project (J. Wang et al. 2012) in a special way.

Previous analysis of the same Bluedisk dataset already shows that the gas richness of a galaxy is linked to the gas richness of its environment. In particular, the satellites of abnormally ${\rm H}{\textsc i}$-rich spirals are themselves abnormally [[H]{}[<span style="font-variant:small-caps;">i</span> ]{}]{}rich (E. Wang et al. 2015). This result may be seen as a new manifestation of the “conformity phenomenon”, whereby the colours of satellites correlate with the colour of central galaxies (Weinmann et al. 2006, Kauffmann et al. 2010, W. Wang et al. 2012). The work of E. Wang et al. (2015) was based on individual [[H]{}[<span style="font-variant:small-caps;">i</span> ]{}]{}detections in the Bluedisk data cubes and, therefore, is limited to galaxies with $\mHI>10^8~\ms$. As previously pointed out by Kauffmann et al. (2010), because the galactic conformity usually extends to scales far beyond dark matter halos, 