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The feedback from an active galactic nucleus (AGN) is frequently invoked as amechanism through which gas can be heated or removed from a galaxy. However,gas fraction measurements in AGN hosts have yielded mixed support for thisscenario. Here, we re-visit the assessment of fgas (=MHI/M*) in z<0.05 AGNhosts in the Sloan Digital Sky Survey (SDSS) using two complementarytechniques. First, we investigate fgas for 75 AGN host galaxies in the extendedGALEX Arecibo SDSS Survey (xGASS), whose atomic gas fractions are complete to afew percent. Second, we construct HI spectral stacks of 1562 AGN from theArecibo Legacy Fast ALFA (ALFALFA) survey, which enables us to extend the AGNsample to lower stellar masses. Both techniques find that, at fixed M*, AGNhosts with log M*>10.2 are HI rich by a factor of ~2. However, this gasfraction excess disappears when the control sample is additionally matched instar formation rate (SFR), indicating that these AGN hosts are actually HInormal. At lower stellar mass, the stacking analysis reveals that AGN hosts areHI poor at fixed stellar mass. In the lowest M* regime probed by our sample,9<log M*<9.6, the HI deficit in AGN hosts is a factor of ~4, and remains at afactor of ~2 even when the control sample is additionally matched in SFR. Ourresults help reconcile previously conflicting results, by showing that matchingcontrol samples by more than just stellar mass is critical for a rigourouscomparison.

Atomic gas fractions in active galactic nucleus host galaxies