Exploring the links between star formation and minor companions around
  isolated galaxies
  Previous studies have shown that galaxies with minor companions exhibit an
elevated star formation rate. We reverse this inquiry, constructing a
volume-limited sample of \simL\star (Mr \leq -19.5 + 5 log h) galaxies from the
Sloan Digital Sky Survey that are isolated with respect to other luminous
galaxies. Cosmological simulations suggest that 99.8% of these galaxies are
alone in their dark matter haloes with respect to other luminous galaxies. We
search the area around these galaxies for photometric companions. Matching
strongly star forming (EW(H{\alpha})\geq 35 \AA) and quiescent (EW(H{\alpha})<
35 \AA) samples for stellar mass and redshift using a Monte Carlo resampling
technique, we demonstrate that rapidly star-forming galaxies are more likely to
have photometric companions than other galaxies. The effect is relatively
small; about 11% of quiescent, isolated galaxies have minor photometric
companions at radii \leq 60 kpc h$^{-1}$ kpc while about 16% of strongly
star-forming ones do. Though small, the cumulative difference in satellite
counts between strongly star-forming and quiescent galaxies is highly
statistically significant (PKS = 1.350 \times10$^{-3}$) out to to radii of \sim
100 h$^{-1}$ kpc. We discuss explanations for this excess, including the
possibility that \sim 5% of strongly star-forming galaxies have star formation
that is causally related to the presence of a minor companion.
