The Dusty Nuclear Torus in NGC 4151: Constraints from Gemini
  Near-Infrared Integral Field Spectrograph Observations
  We have used a near-infrared nuclear spectrum (covering the Z, J, H and K
bands) of the nucleus of NGC 4151 obtained with the Gemini Near-infrared
Integral Field Spectrograph (NIFS) and adaptive optics, to isolate and
constrain the properties of a near-IR unresolved nuclear source whose spectral
signature is clearly present in our data. The near-IR spectrum was combined
with an optical spectrum obtained with the Space Telescope Imaging Spectrograph
which was used to constrain the contribution of a power-law component. After
subtraction of the power-law component, the near-IR continuum is well fitted by
a blackbody function, with $T=1285\pm50 $K, which dominates the nuclear
spectrum -- within an aperture of radius 0$\farcs$3 -- in the near-IR. We
attribute the blackbody component to emission by a dusty structure, with hot
dust mass $M_{\rm HD}=(6.9\pm 1.5) \times10^{-4} {\rm M_\odot}$, not resolved
by our observations, which provide only an upper limit for its distance from
the nucleus of 4 pc. If the reddening derived for the narrow-line region also
applies to the near-IR source, we obtain a temperature $T=1360\pm50 $K and a
mass $M_{\rm HD}=(3.1\pm 0.7) \times10^{-4} {\rm M_\odot}$ for the hot dust.
This structure may be the inner wall of the dusty torus postulated by the
Unified Model or the inner part of a dusty wind originating in the accretion
disk.
