A three-dimensional model of the Orion Nebula
Z. Wen, C. R. O'Dell;
ApJ, 1995, 438, 784
ABSTRACT:We have constructed a geometric model for the Orion Nebula exploiting the fact that most of
the radiation arises from a relatively thin layer of ionized material near
the ionization front on the near side of the giant molecular cloud
OMC-1.
As a first step, an extinction corrected surface brightness map of H alpha
emission was combined with point by point determinations of the electron
density to determine the thickness of the emitting layer across the
nebula.
The second step involved calculation of the geometry that would satisfy
the derived emitting layer thickness constraint, the surface brightness
in H alpha, and the assumption that all of the ionizing radiation comes
from a single star, theta(sup 1) Ori C.
This was done both for the case of a
constant gas density along a line of sight and the more realistic case of an
exponentially decreasing density.
The resulting models show that M42 is a highly
irregular object, with regions in the ionization front where the local slope in
the geometry is steeper producing higher surface brightnesses.
This
model also explains local ionization variations near the Bright Bar and the
brightest region about 40 sec southwest of theta(sup 1) Ori C.
KEYWORDS: astronomical models, h ii regions, molecular clouds, orion nebula, spectral emission, three dimensional models, brightness, ionization, photons
PERSOKEY:region hii, ,
CODE: wen95