The History of Star Formation in Galaxy Disks in the Local Volume as
  Measured by the ACS Nearby Galaxy Survey Treasury
  We present a measurement of the age distribution of stars residing in spiral
disks and dwarf galaxies. We derive a complete star formation history of the
~140 Mpc^3 covered by the volume-limited sample of galaxies in the Advanced
Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST). The total star
formation rate density history is dominated by the large spirals in the volume,
although the sample consists mainly of dwarf galaxies. Our measurement shows a
factor of ~3 drop at z~2, in approximate agreement with results from other
measurement techniques. While our results show that the overall star formation
rate density has decreased since z~1, the measured rates during this epoch are
higher than those obtained from other measurement techniques. This enhanced
recent star formation rate appears to be largely due to an increase in the
fraction of star formation contained in low-mass disks at recent times.
Finally, our results indicate that despite the differences at recent times, the
epoch of formation of ~50% of the stellar mass in dwarf galaxies was similar to
that of ~50% of the stellar mass in large spiral galaxies (z>~2), despite the
observed galaxy-to-galaxy diversity among the dwarfs.
