Quantitative constraints on starburst cycles in galaxies with stellar
  masses in the range 10**8-10**10 Msol
  We have used 4000 \AA\ break and H$\delta_A$ indices in combination with
SFR/M* derived from emission line flux measurements, to constrain the recent
star formation histories of galaxies with stellar masses in the range
10**8-10**10 Msol. The fraction of the total SFR density in galaxies with
ongoing bursts is a strong function of stellar mass, declining from 0.85 at a
stellar mass of 10**8 Msol to 0.25 for galaxies with M* = 10**10 Msol. Low mass
galaxies are not all young. The distribution of half mass formation times for
galaxies with stellar masses less than 10**9 Msol is broad, spanning the range
1-10 Gyr. The peak-to-trough variation in star formation rate among the
bursting population ranges lies in the range 10-25. In low mass galaxies, the
average duration of the burst is comparable to the dynamical time of the
galaxy. Galaxy structure is correlated with estimated burst mass fraction, but
in different ways in low and in high mass galaxies. High mass galaxies with
large burst mass fractions are more centrally concentrated, indicating that
bulge formation is at work. In low mass galaxies, stellar surface mass
densities decrease as a function of F_{burst}. These results are in good
agreement with the observational predictions of Teyssier et al (2013) and lend
further credence to the idea that the cuspy halo problem can be solved by
energy input from multiple starbursts over the lifetime of the galaxy. We note
that there is no compelling evidence for IMF variations in the population of
star-forming galaxies in the local Universe.
