Formation of Raman Scattering Wings around H alpha, H beta and Pa alpha
  in Active Galactic Nuclei
  Powered by a supermassive black hole with an accretion disk, the spectra of
active galactic nuclei (AGNs) are characterized by prominent emission lines
including Balmer lines. The unification schemes of AGNs require the existence
of a thick molecular torus that may hide the broad emission line region from
the view of observers near the equatorial direction. In this configuration, one
may expect that the far UV radiation from the central engine can be Raman
scattered by neutral hydrogen to reappear around Balmer and Paschen emission
lines which can be identified with broad wings. We produce H$\alpha$, H$\beta$
and Pa$\alpha$ wings using a Monte Carlo technique to investigate their
properties. The neutral scattering region is assumed to be a cylindrical torus
specified by the inner and outer radii and the height. While the covering
factor of the scattering region affects the overall strengths of the wings, the
wing widths are primarily dependent on the neutral hydrogen column density
$N_{\rm HI}$ being roughly proportional to $N_{\rm HI}^{1/2}$. In particular,
with $N_{\rm HI}=10^{23}{\rm\ cm^{-2}}$ the H$\alpha$ wings typically show a
width $\sim 2\times 10^4{\rm\ km\ s^{-1}}$. We also find that H$\alpha$ and
Pa$\alpha$ wing profiles are asymmetric with the red part stronger than the
blue part and an opposite behavior is seen for H$\beta$ wings.
