Galaxy Zoo: the dependence of the star formation-stellar mass relation
  on spiral disk morphology
  We measure the stellar mass-star formation rate relation in star-forming disk
galaxies at z<0.085, using Galaxy~Zoo morphologies to examine different
populations of spirals as classified by their kiloparsec-scale structure. We
examine the number of spiral arms, their relative pitch angle, and the presence
of a galactic bar in the disk, and show that both the slope and dispersion of
the M-SFR relation is constant when varying all the above parameters. We also
show that mergers (both major and minor), which represent the strongest
conditions for increases in star formation at a constant mass, only boost the
SFR above the main relation by ~0.3 dex; this is significantly smaller than the
increase seen in merging systems at z>1. Of the galaxies lying significantly
above the M-SFR relation in the local Universe, more than 50% are mergers. We
interpret this as evidence that the spiral arms, which are imperfect
reflections of the galaxy's current gravitational potential, are either fully
independent of the various quenching mechanisms or are completely overwhelmed
by the combination of outflows and feedback. The arrangement of the star
formation can be changed, but the system as a whole regulates itself even in
the presence of strong dynamical forcing.
