Collimation and scattering of the active galactic nucleus emission in
  the Sombrero galaxy
  We present an analysis of a data cube of the central region of M104, the
Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and
report the discovery of collimation and scattering of the active galactic
nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis
with PCA Tomography and spectral synthesis revealed the existence of
collimation and scattering of the AGN featureless continuum and also of a broad
component of the H{\alpha} emission line. The collimation and scattering of
this broad H{\alpha} component was also revealed by fitting the [NII]
{\lambda}{\lambda}6548,6583 and H{\alpha} emission lines as a sum of Gaussian
functions. The spectral synthesis, together with a V-I image obtained with the
Hubble Space Telescope, showed the existence of circumnuclear dust, which may
cause the light scattering. We also identify a dusty feature that may be
interpreted as a torus/disk structure. The existence of two opposite regions
with featureless continuum (P.A. = -18{\deg} +/- 13{\deg} and P.A. = 162{\deg}
+/- 13{\deg}) along a direction perpendicular to the torus/disk (P.A. =
72{\deg} +/- 14{\deg}) suggests that this structure is approximately edge-on
and collimates the AGN emission. The edge-on torus/disk also hides the
broad-line region. The proposed scenario is compatible with the Unified Model
and explains why only a weak broad component of the H{\alpha} emission line is
visible and also why many previous studies detected no broad H\alpha. The
technique used here proved to be an efficient method not only for detecting
scattered light but also for testing the Unified Model in low luminosity AGNs.
