Spatially Resolved Spectroscopic Study of nearby Seyfert Galaxies:
  Implications for a Population of "Missed" Seyferts at High-$\textit{z}$
  We present mosaicked long-slit spectral maps of 18 nearby Active Galactic
Nuclei (AGNs), 2 LINERs, and 4 star-forming galaxies. With the resulting data
cubes taken using the Kast dual spectrograph on the 3 m Shane telescope of the
Lick Observatory, we measure the aperture effects on the spectroscopic
classification of AGNs. With more starlight included in a larger aperture, the
nuclear spectrum that is Seyfert-like may become contaminated. We generated
standard spectroscopic classification diagrams in different observing
apertures. These show quantitatively how the ensemble of Seyferts migrates
toward the H $\scriptsize{\textrm{II}}$ region classification when being
observed with increasing aperture sizes. But the effect ranges widely in
individual active galaxies. Some of the less luminous Seyferts shfit by a large
amount, while some other barely move or even shift in different directions. We
find that those Seyfert galaxies with the fraction of nuclear H$\alpha$
emission lower than 0.2 of the host galaxy, 2-10 keV hard X-ray luminosity
lower than $10^{43}$ erg s$^{-1}$, and the observed nuclear [O
$\scriptsize{\textrm{III}}$] luminosity lower than $10^{40.5}$ erg s$^{-1}$,
are more likely to change activity classification type when the entire host
galaxy is included. Overall, 4 of our 24 galaxies (18 Seyferts) change their
spectral activity classification type when observed with a very large aperture.
