Star Formation Properties of Isolated Blue Compact Galaxies
  We report H$\alpha$ observations of a sample of very isolated blue compact
galaxies (BCGs) located in the direction of large cosmic voids obtained to
understand their stellar population compositions, the present star formation
(SF) properties, and their star formation histories (SFHs). Our observations
were combined with photometric data from the Sloan Digital Sky Survey (SDSS)
and near-infrared data from the Two Micron All Sky Survey (2MASS), wherever
such data were available. The combined data sets were compared with predictions
of evolutionary synthesis models by Bruzual & Charlot (2003a, 2003b). Current
star formation rates (SFRs) were determined from the H$\alpha$ measurements,
and simplified star formation histories were derived from broad-band and
H$\alpha$ photometry and comparisons with the models. We found that the star
formation rates range within 0.1--1.0 M$_{\odot}$ yr$^{-1}$, with a median rate
of 0.6 M$_{\odot}$ yr$^{-1}$. The observed galaxy colours are better explained
by the combination of a continuous SF process with a recent instantaneous SF
burst, than by a combination of several instantaneous bursts, as has been
suggested previously. We compare our results for the star formation rate of the
sample galaxies with that of samples of dwarf galaxies in the Virgo cluster and
find that the BCGs have significantly stronger SFRs. The BCGs follow the
correlation between H$\alpha$ emission and starlight found for dwarf galaxies
in the Virgo Cluster and for other BCGs.
