Characterizing the WISE-selected Heavily Obscured Quasar Population with
  Optical Spectroscopy from the Southern African Large Telescope
  We present the results of an optical spectroscopic survey of 46 heavily
obscured quasar candidates. Objects are selected using their mid-infrared
(mid-IR) colours and magnitudes from the Wide-Field Infrared Survey Explorer
(WISE) and their optical magnitudes from the Sloan Digital Sky Survey (SDSS).
Candidate Active Galactic Nuclei (AGNs) are selected to have mid-IR colours
indicative of quasar activity and lie in a region of mid-IR colour space
outside previously published X-ray based selection regions. We obtain optical
spectra for our sample using the Robert Stobie Spectrograph on the Southern
African Large Telescope. Thirty objects (65%) have identifiable emission lines,
allowing for the determination of spectroscopic redshifts. Other than one
object at $z\sim2.6$, candidates have moderate redshifts ranging from $z=0.1$
to $0.8$ with a median of 0.3. Twenty-one (70%) of our objects with identified
redshift (46% of the whole sample) are identified as AGNs through common
optical diagnostics. We model the spectral energy distributions of our sample
and found that all require a strong AGN component, with an average intrinsic
AGN fraction at 8$\,\mu$m of 0.91. Additionally, the fits require large
extinction coefficients with an average $E(B-V)_\textrm{AGN} = 17.8$ (average
$A(V)_\textrm{AGN} = 53.4$). By focusing on the area outside traditional mid-IR
photometric cuts, we are able to capture and characterise a population of
deeply buried quasars that were previously unattainable through X-ray surveys
alone.
