Imaging Extended Emission-Line Regions of Obscured AGN with the Subaru
  Hyper Suprime-Cam Survey
  Narrow-line regions excited by active galactic nuclei (AGN) are important for
studying AGN photoionization and feedback. Their strong [O III] lines can be
detected with broadband images, allowing morphological studies of these systems
with large-area imaging surveys. We develop a new technique to reconstruct the
[O III] images using the Subaru Hyper Suprime-Cam (HSC) Survey aided with
spectra from the Sloan Digital Sky Survey (SDSS). The technique involves a
careful subtraction of the galactic continuum to isolate emission from the [O
III]$\lambda$5007 and [O III]$\lambda$4959 lines. Compared to traditional
targeted observations, this technique is more efficient at covering larger
samples with less dedicated observational resources. We apply this technique to
an SDSS spectroscopically selected sample of 300 obscured AGN at redshifts 0.1
- 0.7, uncovering extended emission-line region candidates with sizes up to
tens of kpc. With the largest sample of uniformly derived narrow-line region
sizes, we revisit the narrow-line region size-luminosity relation. The area and
radii of the [O III] emission-line regions are strongly correlated with the AGN
luminosity inferred from the mid-infrared (15 $\mu$m rest-frame) with a
power-law slope of $0.62^{+0.05}_{-0.06} \pm 0.10$ (statistical and systemic
errors), consistent with previous spectroscopic findings. We discuss the
implications for the physics of AGN emission-line region and future
applications of this technique, which should be useful for current and
next-generation imaging surveys to study AGN photoionization and feedback with
large statistical samples.
