The Effect of Structure and Star Formation on the Gas Content of Nearby
  Galaxies
  We revisit the main HI-to-stellar mass ratio (gas fraction) scaling
relations, taking advantage of the HI spectral stacking technique to understand
the dependence of gas content on the structural and star formation properties
of nearby galaxies. This work uses a volume-limited, multi-wavelength sample of
~25,000 galaxies, selected according to stellar mass (10^9 M_sol < M_* <
10^11.5 M_sol) and redshift (0.02 < z < 0.05) from the Sloan Digital Sky
Survey, and with HI data from the Arecibo Legacy Fast ALFA survey. We bin
according to multiple parameters of galaxies spanning the full gas-poor to
-rich regime in order to disentangle the dominance of different components and
processes in influencing gas content. For the first time, we show that the
scaling relations of gas fraction with stellar mass and stellar surface density
are primarily driven by a combination of the underlying galaxy bimodality in
specific star formation rate and the integrated Kennicutt-Schmidt law. Finally,
we produce tentative evidence that the timescales of HI depletion are dependent
upon galaxy mass and structure, at fixed specific star formation rate.
