Nuclear starburst activity induced by elongated bulges in spiral
  galaxies
  We study the effects of bulge elongation on the star formation activity in
the centers of spiral galaxies using the data from the Sloan Digital Sky Survey
Data Release 7. We construct a volume-limited sample of face-on spiral galaxies
with $M_r < -$19.5 mag at 0.02 $\leq z <$ 0.055 by excluding barred galaxies,
where the aperture of the SDSS spectroscopic fibre covers the bulges of the
galaxies. We adopt the ellipticity of bulges measured by Simard et al. (2011)
who performed two-dimensional bulge+disc decompositions using the SDSS images
of galaxies, and identify nuclear starbursts using the fibre specific star
formation rates derived from the SDSS spectra. We find a statistically
significant correlation between bulge elongation and nuclear starbursts in the
sense that the fraction of nuclear starbursts increases with bulge elongation.
This correlation is more prominent for fainter and redder galaxies, which
exhibit higher ratios of elongated bulges. We find no significant environmental
dependence of the correlation between bulge elongation and nuclear starbursts.
These results suggest that non-axisymmetric bulges can efficiently feed the gas
into the centre of galaxies to trigger nuclear starburst activity.
