PAH emission from the dust lane of an elliptical galaxy with the Spitzer
  IRS
  Spitzer and AKARI observations have found that polycyclic aromatic
hydrocarbons (PAHs) are present in nearby elliptical galaxies, but their
spatial distributions are still unknown. In order to investigate their
distributions, we performed deep spectral mapping observations of the
PAH-detected elliptical galaxy NGC4589, a merger remnant with a minor-axis
optical dust lane. As a result, we obtain clear evidence that the PAH 11.3 um
emission comes predominantly from the dust lane of the galaxy. We also detect
molecular hydrogen line emissions from the dust lane. The PAH 17 um emission is
distributed differently from the PAH 11.3 um emission, and more similarly to
the dust continuum emission. From their distinctive distributions, we suggest
that the PAHs responsible for the 11.3 um feature are secondary products
through the evolution of the ISM brought in by the merger.
